| 1. |
- Aljetlawi, A A, et al.
(författare)
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Effect of food and sediment pre-treatment in experiments with a deposit-feeding amphipod, Monoporeia affinis
- 2000
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Ingår i: Journal of Experimental Marine Biology and Ecology. - Umea Univ, Dept Ecol & Environm Sci, SE-90187 Umea, Sweden.. - 0022-0981 .- 1879-1697. ; 249:2, s. 263-280
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigated the effects of different pre-treatments of the sediment, and the effect of daily addition of fresh phytoplankton, on the growth and survival of 1-year-old (1 +) individuals of the deposit feeder Monoporeia affinis (Amphipoda). We used three different types of sieved sediment: pre-frozen muddy clay, non-pre-frozen muddy clay, and fine sand. The muddy clay contained phytoplankton originating from the surface sediment sampled in the field during the late spring bloom. No phytoplankton was initially present in sand. The experiment lasted for 18 days. M. affinis responded to the daily phytoplankton addition by increasing growth. Phytoplankton addition had no significant effects on the survival of M. affinis. Upon phytoplankton addition, the sandy and non-frozen muddy clay gave similar growth and survival responses. In contrast, the pre-frozen sediment resulted in significantly lower growth and survival. The growth was negative in all treatments without phytoplankton. Thus, the high initial chlorophyll content in the muddy clay was not of sufficient quality or concentration to allow a positive growth response in M. affinis. The growth of M. affinis was significantly correlated with the reduction of the chlorophyll. Our results indicated that M. affinis is capable of assimilating settled phytoplankton with no, or only a few days' time delay. (C) 2000 Elsevier Science BN: All rights reserved.
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| 2. |
- Macia, Adriano, et al.
(författare)
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Thorn fish Terapon jarbua (Forskål) predation on juvenile white shrimp Penaeus indicus H. Milne Edwards and brown shrimp Metapenaeus monoceros (Fabricius) : the effect of turbidity, prey density, substrate type and pneumatophore density
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981 .- 1879-1697. ; 291:1, s. 29-56
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Tidskriftsartikel (refereegranskat)abstract
- A series of laboratory experiments was conducted at Inhaca Island Marine Biological Station, Mozambique, in order to assess the separate effects of turbidity, prey density, substrate type, pneumatophore density, and the combined effects of turbidity with the latter three, on rate of predation by the thorn fish Terapon jarbua (Forskål, 1775) on white shrimp Penaeus indicus and brown shrimp Metapenaeus monoceros. Significant interactions between turbidity and the other three factors on shrimp predation for both prey species were detected. Regardless of prey density, increasing turbidity decreased predation on P. indicus, but not on M. monoceros, for which increasing densities reduced the protective effect of turbidity. Increasing prey density increased predation on P. indicus in clear water, and increased predation on M. monoceros in low and high, but not in intermediate turbidity or clear water. The presence of a substrate suitable for burying decreased predation on M. monoceros in clear water, but not in the turbidity levels used. In clear water, solely sandy-shell substrate afforded protection to P. indicus, while in turbid water, no substrate offered significant protection and muddy substrate even increased prey vulnerability to fish probably as a result of increased preys' locomotor activity. Raising pneumatophores density seems to lower the protective value of turbidity for both species. In clear water, only low and high structure density provided a deterrent effect on predation on P. indicus; in turbid water, intermediate and higher structure density increased predation. Increasing structural complexity reduced predation on M. monoceros linearly in clear water; but in low turbid water it increased. In high turbid waters, the increase was only significant in intermediate pneumatophore density. High structural complexities impair the pursuing capacity of fish and thus decreased predation rates. The results indicate that the effective provision of shelter of different habitats depends not only on the various environmental parameters analysed, but also on the way they interact and on the behaviour of prey and predator as well.
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| 3. |
- Kamenos, Nicholas A., et al.
(författare)
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Attachment of the juvenile queen scallop (Aequipecten opercularis (L.)) to Maerl in mesocosm conditions; juvenile habitat selection
- 2004
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 306:2, s. 139-155
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Tidskriftsartikel (refereegranskat)abstract
- Substratum un-acclimated juvenile queen scallops (Aequipecten opercularis) (< 18 mm and 1830 mm shell height) were released in equal numbers onto pristine live maerl (PLM), impacted dead maerl (IDM), gravel and sand in choice chambers. Their habitat selection was monitored over a 4-day period in control and predator treatments (utilising Asterias rubens L. and Carcinus maenas (L.)). Microhabitat use of PLM by juvenile queen scallops and the presence of cues in live maerl were also investigated.In control and predator treatments juvenile queen scallops were observed to attach preferentially to PLM than IDM, gravel or sand. Juvenile queen scallops were observed to maintain a more exposed attachment site in the absence of predators but sought refuge within and between maerl nodules in the presence of both predators. Smaller queen scallops (< 18 mm shell height) were more efficient at utilising maerl thalli as a refuge. Juvenile A. opercularis showed hierarchical cue responses mediated by predator presence, i.e. responding favourably to a factor associated with live maerl presence irrespective of heterogeneity in the absence of predators but favourably to higher maerl heterogeneity in their presence. If they also preferentially attach to PLM in the field, at some sites where PLM grounds cover large areas, they may thus be considered to constitute 'nursery areas'. Habitat attachment preference appears to be predetermined and not a result of localised predator avoidance; however, habitat usage changes in the presence of predators. Maerl beds have been shown to be easily damaged by scallop dredging in Scotland and if such nursery areas are being destroyed extensively in the field, this could damage recruitment to localised adult populations.
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| 4. |
- Kamenos, Nicholas A., et al.
(författare)
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Maerl grounds provide both refuge and high growth potential for juvenile queen scallops (Aequipecten opercularis L.)
- 2004
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier. - 0022-0981 .- 1879-1697. ; 313:2, s. 241-254
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Tidskriftsartikel (refereegranskat)abstract
- Human damage to biogenic substrata such as maerl has been receiving increasing attention recently. Maerl forms highly biodiverse and heterogeneous habitats composed of loose-lying coralline red algae, which fulfil nursery area prerequisites for queen scallops (Aequipecten opercularis) and other invertebrates. The benefits obtained by queen scallops utilising maerl were poorly understood, so we used both laboratory predation and field tethering experiments to investigate the refuge and growth potential provided by pristine live maerl (PLM) grounds over other common substrata. In aquaria, more juvenile queen scallops (<35 mm shell height) survived on PLM than on gravel substrata in the presence of the crab Carcinus maenas or the starfish Asterias rubens. Field tethering experiments indicated similar survivorship of juvenile queen scallops on PLM and gravel; additionally, their growth rates were similar on both substrata. PLM allows scallops to seek refuge from predators and position themselves to optimise their food supply. Other bivalve refugia have been shown to provide poor food supply as a consequence of their high heterogeneity, yet maerl grounds provide a 'win-win' scallop nursery area coupling refuge availability with high food supply.
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| 5. |
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| 6. |
- Morford, Jennifer L., et al.
(författare)
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Sampling marine pore waters for Mn, Fe, U, Re and Mo: Modifications on diffusional equilibration thin film gel probes
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285-286, s. 85-103
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Tidskriftsartikel (refereegranskat)abstract
- Pore water metal profiles are important for identifying redox horizons and understanding trace metal geochemical cycling. The challenges of pore water sampling for trace metals are minimizing disturbance, especially at the sediment–water interface, and minimizing oxidation during sampling. We are investigating diffusional equilibration in thin films (DET) probes for obtaining pore water profiles. Our goal is to use probes for redox-sensitive trace metals U, Re and Mo, in addition to Mn and Fe, in coastal marine areas. Initial solution equilibration tests and laboratory core incubation experiments suggest that equilibration times for probes in sediments are approximately 24–48 h. Control tests suggest that the incubation does not alter the redox conditions in the pore waters. Pore water profiles from cores sampled by slicing, centrifuging and filtering (in a nitrogen atmosphere) and from probes are similar. Two modifications on the gel probe design were tested to determine their impact. (1) PVC wedges were attached to the backs of probes to increase the contact between sediments and the probe surface and to reduce the risk of forming channels along the probe surface, which might allow vertical pore water transport. Lower Fe concentrations were measured from probes without PVC wedges, but other metal profiles were similar. (2) A modified face frame was removed from the front of a probe, to reduce disturbance of the sediments during insertion and to increase the contact between the sediments and probe surface. Probes with modified face frames did not have increasing U and Mo concentrations with depth, whereas two of the three probes without face frames did have increasing concentrations. Increasing U and Mo concentrations at depth may be reflecting the influence of irrigating burrows and their supply of oxygen to reduced sediments, which could oxidize previously reduced metals. The distribution of burrows is heterogeneous and resulting profiles would also be expected to be heterogeneous in their response. Differences between probe profiles and sliced/centrifuged profiles are examined to gain insight into possible sampling artifacts. Peaks in the Re sliced/centrifuged profiles suggest a large Re flux to the overlying waters, which is neither calculated from probe profiles nor measured in benthic chamber samples. It is possible that heterogeneity at the sampling site in Buzzards Bay resulted in these differences; however, it is also possible that centrifugation releases Re from pore structures that would not be measured with less intrusive sampling methods, such as gel probes or benthic chambers.
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| 7. |
- Cervin, Gunnar, 1967, et al.
(författare)
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Effects of small-scale disturbances of canopy and grazing on intertidal assemblages on the Swedish west coast
- 2004
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 302:1, s. 35-49
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Tidskriftsartikel (refereegranskat)abstract
- The effects of small-scale disturbances (80 x 30-cm plots) of canopy and grazers on intertidal assemblages were investigated in this 4-year experiment on sheltered rocky shores on the Swedish west coast. Canopy disturbances due to ice scouring were mimicked by removal of adult plants of the seaweed Ascophyllum nodosum (L) Le Joli. Density of the main epilithic grazing gastropods, Littorina spp., was lowered by exclosure and handpicking. Based on earlier experiments in other areas, the general hypothesis was that canopy removal and grazer exclosure, alone or in combination, should increase the recruitment of A. nodosum or other fucoid juveniles, and change the structure of the understorey assemblage. There was an effect of canopy removal on the development of this assemblage, lasting for more than 31 months. Both increased and decreased abundances of species were found as short-term effects, but there was also a longer-term effect with increased abundance. Grazer exclosure was only effective in combination with canopy removal, causing a short-term increase in ephemeral green algae. Short-term effects of canopy removal were also the increase in recruitment of Semibalanus balanoides (Linnaeus) and the decrease of the red alga Hildenbrandia rubra (Sommerfelt) Meneghini. Fast recruitment and growth of fucoid species (Fucus serratus L. and F vesiculosus L.) restored the canopy and conditions of the understorey within 18 months. Thus, the canopy removal changed the physical conditions for the understorey, making it possible for other species to coexist in this community. Surprisingly, no effect of canopy removal or grazer exclusion was found on the recruitment of juvenile A. nodosum, neither by canopy removal nor grazer exclosure. The lack of such effects might be due to the early mortality caused by other grazers (small, mobile crustaceans), or to the low density of periwinkles on these shores. However, despite the patchy and generally low recruitment of A. nodosum juveniles, observations suggested that the cover of A. nodosum in manipulated patches would return to initial levels, either by recruitment or regrowth of small holdfasts and from growth of edge plants. (C) 2003 Elsevier B.V. All rights reserved.
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| 8. |
- Dahlström, Mia, et al.
(författare)
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Surface wettability as a determinant in the settlement of the barnacle Balanus Improvisus (DARWIN)
- 2004
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 305:2, s. 223-232
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Tidskriftsartikel (refereegranskat)abstract
- Several studies have shown that the initial surface wettability, is of importance in the settlement of macrofouling larvae such as barnacles, bryozoans and hydroids in the field as well as in laboratory assays. In this study we present results from laboratory assays using hydrophilic and hydrophobic polystyrene (PS) and cyprid larvae of Balanus improvisus (Darwin). The results obtained differ markedly from those reported for the barnacle Balanus amphitrite (Darwin), where a high surface wettability seemed to be preferred for settlement. Our results show that a surface with intermediary wettability (hydrophilic PS) reduced settlement by 38% as compared to surfaces of low wettability (hydrophobic PS) during an 8-day period. During the experiment, the wettability in the hydrophilic PS dishes was not significantly changed as measured by advancing contact angle with mQ water. Over an 8-day period wettability of the hydrophobic PS dishes approached that of the hydrophilic PS surfaces. We further conducted experiments with highly hydrophilic and highly hydrophobic methylsilane-treated glass surfaces with known chemistry. In this experiment, the settlement of cyprid larvae was completely inhibited by the high wettability surfaces. Contact angle measurements revealed that the wettability during the length of the experiment of the hydrophilic glass surfaces was not significantly altered. We conclude by these experiments that even an intermediate wettability can significantly affect the overall settlement success of the barnacle B. improvisus. The mechanism by which the settlement is impeded might be biologically mediated through the recognition by cyprid larvae of the molecular composition of the surface when the cyprid reverts to the settlement phase, i.e. when swimming behaviour is abandoned in favour of surface exploration, or it is mediated by physicochemical forces acting between the surface and the larval body or the larval antennules. (C) 2004 Published by Elsevier B.V.
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| 9. |
- Gilbert, F., et al.
(författare)
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2-D optical quantification of particle reworking activities in marine surface sediments
- 2003
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Ingår i: JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY. - 0022-0981. ; 285, s. 251-263
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Tidskriftsartikel (refereegranskat)abstract
- Particle and solute transport by faunal activities may significantly influence rates and pathways of organic matter mineralization during early diagenesis in surface sediments. One of the most frequently utilized techniques to quantify benthic biological reworking activities involves the calculation of a biodiffusion coefficient (D-b) estimated from model predictions of 1-D tracer distribution patterns. This technique is labor-intensive and time-demanding. Furthermore, it is normally used for measurements over several days and averages overall transport mechanisms from 3-D to 1-D on a cm scale. In the frame of this work, we developed a new technique based on the nondestructive screening of fluorescent particles (luminophores) using optical discrimination and CCD camera detection of fluorescence (2-D). At a site characterized by a dense population of the brittle star Amphiura filiformis and a high biodiffusion coefficient (obtained from 1-D distributions; D-b = 3 5.5 +/- 3.7 cm(-2) year(-1); n = 3), the optical reworking coefficient (ORC), estimated from the 2-D luminophore distribution patterns, was calculated (ORC = 27.4 +/- 9.1 DeltaQ cm(-2) h(-1); n=24). A nondestructive 2-D approach to quantify particle reworking may provide a powerful and complementary tool to further understand particle transport by the benthic fauna in surface sediments. The optical technique for 2-D detection of luminophores is relatively fast and easy to perform, with the ability to detect small scale (mm) particle movements on a time resolution of minutes or less. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 10. |
- Jenkins, S. R., et al.
(författare)
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Spatial and temporal variation in settlement and recruitment of the intertidal barnacle Semibalanus balanoides (L.) (Crustacea : Cirripedia) over a European scale
- 2000
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 243:2, s. 209-225
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Tidskriftsartikel (refereegranskat)abstract
- Variation in the level of settlement and recruitment in the intertidal barnacle Semibalanus balanoides was studied using a hierarchical sampling programme. The effect of three spatial scales, 10s of metres (sites), 1000s of metres (shores) and 100s of kilometres (locations), was determined. The largest spatial scale represented the distance between four widely separated locations, Sweden, the Isle of Man, SW Ireland and SW England, covering a. large part of the range of S. balanoides in Europe. Temporal variation was determined by comparison between two years, 1997 and 1998. The settlement period of S. balanoides varied in length and timing, being earlier and shorter at the most northerly location, Sweden. The duration of settlement showed little difference among shores within locations, but the pattern of settlement did vary. Estimates of total settlement throughout the settlement period and of recruitment at the end of this period both showed substantial variation among locations which was dependent on the year of study. There was little consistency in the ranking of locations between the two years. Recruitment showed significant variation I the lower spatial scales of shore and site. In addition, examination of variance components showed a high degree of variation between replicates within sites in 1997. There was a significant relationship between settlement and recruitment at three of the four locations. Across all locations variation in settlement explained between 29 and 99% of variation in recruitment. However, locations showed distinct differences in the level of post-settlement survival. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 11. |
- Krång, Anna Sara, 1972, et al.
(författare)
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The ability of the amphipod Corophium volutator (Pallas) to follow chemical signals from con-specifics
- 2004
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981. ; 310:2, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- The amphipod Corophium volutator (Pallas) is a tube-dwelling species that only occasionally leaves its burrow. Animals that do crawl on the sediment are mainly males, apparently in search of females. This study was designed to determine whether C volutator males and females release chemical signals that attract con-specifics, and if so, whether these signals are gender specific. Laboratory experiments were conducted on the over-wintering generation during their reproductive season, using a Y-maze choice test apparatus. The results show that C volutator females release chemical signals that attract males. In the field, the attractant may guide males in search of burrowed females. In addition, male odour tends to attract males, while females do not follow chemical signals from con-specifics. We thereby show, on gender-specific chemical attraction of this species. (C) 2004 Elsevier B.V. All rights reserved.
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| 12. |
- Lindegarth, Mats, 1965, et al.
(författare)
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A manipulative experiment to evaluate predicted changes in intertidal, macro-faunal assemblages after contamination by heavy metals
- 2002
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 274:1, s. 41-64
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Tidskriftsartikel (refereegranskat)abstract
- Concentrations of heavy metals (zinc, copper and lead) were manipulated experimentally to test the hypotheses about effects on intertidal, soft-sediment assemblages of animals in two sand-flats in Port Hacking, Australia. Hypotheses about changes in the structure and composition of whole assemblages and changes in mean abundance and variability of individual taxa were tested. Specific hypotheses were derived a priori from repeated observations of assemblages in urban and non-urban areas of Port Hacking. After manipulation. concentrations of metals were similar to those in sediments near urban areas, Nevertheless, responses of assemblages to the increased concentrations of metals were weak. Polychaetes, spionids and amphipods responded to experimental treatments. Changes were, however, not consistent among times and places and generally not in agreement with what had been predicted. Significant spatial and temporal variability were detected for all variables investigated. Increased concentrations of metals did not affect variability or overall structure of assemblages. Thus, there was little evidence that increased concentrations of metals caused benthic assemblages in pristine areas to become more similar to those in areas contaminated by human activities, Several potential explanations for the discrepancy between previously observed correlative patterns and the results presented here arc discussed. These include a critical assessment of different aspects of the experimental study, such as lack of statistical power, insufficient basis for prediction, artefacts due to experimental procedures and issues to do with the difference between evidence based on correlation and manipulation. Explicit comparisons showed that there were significant effects of physical disturbance due to repeated sampling and that assemblages of animals at the start of the experiment were different from those previously observed in uncontaminated areas. These observations were surprising and made interpretation more difficult, Nevertheless, it is possible that the metals investigated really contribute only marginally to previously observed differences between urban and non-urban areas, Repeated comparisons between observations of patterns and manipulative experiments like these can only improve the basis for prediction and the power of current mechanistic models. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 13. |
- Lindegarth, Mats, 1965, et al.
(författare)
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Interpreting large-scale experiments on effects of trawling on benthic fauna: an empirical test of the potential effects of spatial confounding in experiments without replicated control and trawled areas
- 2000
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 245:2, s. 155-169
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Tidskriftsartikel (refereegranskat)abstract
- Disturbances due to trawling and dredging is a serious threat to assemblages of benthic marine animals. We tested hypotheses about effects of trawling on benthic assemblages in a manipulative field experiment, using gear and intensities relevant to future management of trawling in a Swedish fjord. Three trawled and three control sites were sampled at several times before and after trawling was initiated. This paper describes how conclusions about effects of trawling might differ between experiments involving replicate sites and experiments using only one trawled and one control site, as in several recent studies. Analyses Df selected taxa showed that abundances of many species changed differently among control sites. Differences in temporal change between pairs of single trawled and control sites were also frequent. Neither the quantitative nor the qualitative nature of differences between treatments could, however, be coherently interpreted among the different combinations of trawled and control sites. This is consistent with results obtained from analyses using all sites, which showed no consistent effects of trawling on any of these taxa. These results provide empirical evidence that spatial confounding may cause serious problems to formal interpretation of experiments, which use only one control and one trawled area. Such potential problems can best be solved by ensuring that the study incorporates more than one control site. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 14. |
- Nilsson, Hans C., et al.
(författare)
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Effects on marine sedimentary habitats of experimental trawling analysed by sediment profile imagery
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285, s. 453-463
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Tidskriftsartikel (refereegranskat)abstract
- Demersal trawling causes significant impact on marine benthic habitats including sediment biogeochemistry and faunal composition. To examine the effect of shrimp trawling on benthic sedimentary habitats a replicated Before/After (B/A) experiment was performed in the Gullmarfjord, Western Sweden, after 6 years protection against trawling activities. The experimental area was randomly divided into three control transects and three trawling transects each similar to 1.5 km long. The experimental fishery activity was designed to mimic the extent and the trawling procedure used before the banning with 80 hauls per site and year. All transects were sampled three times in 1996 before the experimental trawling activity was started, and three times during the experimental trawling activity in the autumn of 1997. Along each transect, 10 replicated sediment profile images (SPIs) were taken randomly at each sampling. The status of the sedimentary habitat was assessed by the parameterisation of a benthic habitat quality (BHQ) index combining sediment surface and subsurface variables and the redox conditions observed in the SPIs. A significant interaction between B/A and treatment was observed in mean BHQ-index. Changes of the BHQ-indices were larger in trawled areas than the natural variation in the experimental area. Mean BHQ-indices in trawled transects were lower than in control transects after the experimental trawling activity was started. In about 43% of the SPIs a severe mechanical disturbance was observed, which introduced a significantly increased spatial variance of BHQ-indices in trawled areas compared to control areas. (C) 2002 Elsevier Science B.V All rights reserved.
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| 15. |
- Osterling, M., et al.
(författare)
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Effects of filamentous green algal mats on benthic macrofaunal functional feeding groups
- 2001
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 263:2, s. 159-183
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Tidskriftsartikel (refereegranskat)abstract
- A field experiment investigating the structuring effect of filamentous green algae on macrofaunal abundance, including functional feeding groups, was performed in a shallow (1 m) soft bottom bay on the Swedish West Coast. Temporal macrofaunal changes were investigated at three occasions under simulated moderate algal disturbance, using algal filled net-bags attached over the sediment. The moderate algal disturbance was also compared to a simulated high algal disturbance where cages were filled with algae. Abundance of suspension feeders and surface detrivores decreased significantly in the sediment after 3 weeks of exposure to high algal disturbance in cages compared to control sediment, but did not change in abundance from moderate disturbance under algal net-bags after this time. However, total macrofauna, suspension feeders and surface detrivores had significant lower abundance in the sediment under algal net-bags compared to controls, when all three occasions were included. Total abundance per unit area in the algae and its underlying sediment was significantly higher in the net-bag treatment compared to total macrofauna. in algal cages and controls. This was mainly due to high abundance among algae. Burrowing detrivores and predators had higher abundance among algae in the net-bags compared to algae in the cages. High abundance of macrofauna recorded among algae in the net-bag treatment could be due to filtering of larvae, post settlement redistribution or vertical migrations. In a laboratory experiment, juvenile Cerastoderma spp. and Corophium volutator migrated vertically into filamentous algae from sediment covered by an algal mat. C. volutator and adult Cerastoderma edule also had the ability to perform small-scale horizontal migrations from algae covered sediment. Suspension feeding bivalves are major contributors to production of the infauna in shallow soft bottoms, are important food for epibenthic predators and may functionally stabilise shallow marine soft bottoms. Decreases in recruitment and abundance of such an important functional group may thereby alter function and trophic relationships on shallow soft bottoms. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 16. |
- Rosenberg, Rutger, 1943, et al.
(författare)
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Effects of demersal trawling on marine sedimentary habitats analysed by sediment profile imagery
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285, s. 465-477
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Tidskriftsartikel (refereegranskat)abstract
- Demersal trawling causes one of the most widespread physical and biological changes in marine shallow and shelf sedimentary habitats: trawl otter boards may create furrows in the sediment surface, while trawl nets and attached weights scrape the sediment surface. As a consequence, benthic animals are disturbed or killed, and resuspension of particles increase. The impact of trawling on benthic animals has traditionally been analysed by changes in species composition and abundance, whereas frequency and distribution of trawl tracks are frequently analysed by side-scan sonar. We have used sediment profile images (SPIs) (30 x 22 cm) and observed furrows and other physical disturbances on the sediment surface that we attribute to trawling. In a manipulative experimental trawl study in Sweden (BACI design), significant impacts were found in trawled benthic habitats (73-93 m deep) compared with pre-trawling conditions and with reference areas. In particular, furrows from trawl boards had a severe ecological impact. In the Gulf of Lions (northwest Mediterranean), similar patterns were observed in the vast majority of 76 images taken at random at depths between 35 and 88 m in four different areas. Epifauna and polychaete tubes were generally either rare or not observed at all on trawled sediment surfaces. Burrows and feeding voids were, however, frequently present in some trawled areas and seemed to be comparatively less affected. Such biogenic structures in the sediment were generally associated with rather deep (3-4 cm) mean apparent redox profile discontinuities (aRPDs), which were measured digitally as the visible division zone between oxidised (sub-oxic) and reduced sediments. Increased roughness caused by the trawl boards acting on the sediment surface, e.g. depressions and protrusions, could have effects on sediment solute fluxes. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 17. |
- Solan, M., et al.
(författare)
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Towards a greater understanding of pattern, scale and process in marine benthic systems: a picture is worth a thousand worms
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 285, s. 313-338
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Tidskriftsartikel (refereegranskat)abstract
- Historically, advances in our knowledge of benthic community structure and functioning have necessarily relied upon destructive sampling devices (grabs, cores, anchor dredges, etc.) that lose valuable contextual information in the process of sampling. In the last 40 years, instrumentation capable of measuring dynamic events and/or processes within and immediately above the seafloor has been developed that facilitates the collection of ecological information. Of these, both acoustic and optical imaging devices have played a significant role in revealing much about the physiology and behaviour of, and interactions between benthic species, and the sedimentary habitat in which they reside. While a number of reviews have separately considered the methodological and technical aspects of imaging technologies, the collective contribution that imaging has made to benthic ecology has received less attention. In this short review, we attempt to highlight key instances over the last 40 years where either acoustic or optical-based imaging techniques have provided new ecological insights and information about fine-grained sedimentary environments. In so doing, we focus on the ecological advances that have formed the precursor to current research efforts and introduce some of the latest revelations from appropriate and emerging imaging applications. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 18. |
- Spicer, J. I., et al.
(författare)
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Developmental changes in the responses of O-2 uptake and ventilation to acutely declining O-2 tensions in larval krill Meganyctiphanes norvegica
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 207-218
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Tidskriftsartikel (refereegranskat)abstract
- The effect of exposure to acutely declining oxygen tensions on O-2 uptake (Mo-2) and ventilation has been investigated in different larval stages of Northern krill Meganyctiphanes norvegica (calytopis III/ early furcilia I, late furcilia I, furcilia III and V). An ability to regulate Mo-2 during acutely declining P-O2 began to appear about furcilia III (critical O-2 tension or P-c = 15.4 +/- 0.73 kPa) and had improved by furcilia V (P-c= 12.6 +/- 0.39 kPa). Hypoxia-related hyperventilation was achieved by an increase in pleopod (but not thoracic limb) activity (P-c similar to 11 kPa), a sensitivity which also appeared at, or just before, furcilia V even though an earlier stage (furcilia III) had a full compliment of functional setose pleopods. While this regulatory ability appeared as the gills were beginning to form, furcilia V is still early in gill ontogeny compared with adults. Preexposure to very moderate hypoxia (60% and 70% O-2 (saturation) of furcilia III and V resulted in substantial mortality, but where it did not (furcilia V, 80% O-2 saturation), there was no effect of keeping krill at this P-O2 on either M-O2 or ventilation, suggesting that the development of respiratory regulation in M. norvegica is not open to environmental influence in the same way as for other crustaceans. We suggest that ontogeny of pleopod control provides furcilia V+ with both a stronger means of propulsion, allowing the ontogeny of DVM but also with an ability to regulate M-O2 during exposure to acutely declining P(O2)s. The onset of respiratory regulation (furcilia V) preceded the onset of DVM (furcilia VI+). As pleopod ontogeny is associated intimately with the ontogeny of DVM and respiratory regulation, in the Gullmarsfjord this co-occurrence is fortuitous as krill can be required during DVM to migrate into hypoxic water which they are not equipped to deal with, in physiological terms, before furcilia V. (C) 2003 Elsevier B.V. All rights reserved.
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| 19. |
- Spicer, J. I., et al.
(författare)
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Does the development of respiratory regulation always accompany the transition from pelagic larvae to benthic fossorial postlarvae in the Norway lobster Nephrops norvegicus (L.)?
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 219-243
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Tidskriftsartikel (refereegranskat)abstract
- The ability to regulate O-2 uptake during exposure to acutely declining PO2S co-occurred with metamorphosis from a planktonic to a benthic existence in the Norway lobster Nephrops norvegicus when cultured under normoxic conditions in the laboratory. The onset of this regulation appears to be related to the presence of a hypoxia-related hyperventilation of extrabranchial exchange surfaces (telson/uropods) by the pleopods and a shift from a low to a high He O-2 affinity. This co-occured with a dramatic calcification of the exoskeleton at metamorphosis, which will restrict gas exchange over the general body surface. Evidence marshalled here points to a shift from a pleopod-based, hypoxia-related, hyperventilation of the uropods/telson as gas exchange surfaces to, in later postlarval stages, a scaphognathitc-based response, where the gills are the main areas for gas exchange. This is the first time that experimental evidence has been put forward for the use of uropods/telson by larval lobsters as extrabranchial gas exchange surfaces. Pre-exposure of larval and postlarval N. norvegicus to reduced P-O2, both in the laboratory and in the field, resulted in the "adult" pattern of M-O2, regulation present during exposure to declining P-O2 being established before metamorphosis. Bringing the ontogeny of this regulation forward in the development itinerary was to some extent a result of a shift from a low to a high He O-2 affinity well before metamorphosis and an increase in the magnitude of the hypoxia-related hyperventilatory response in the planktonic larval stages. Thus, the development of respiratory regulation does not always accompany the transition from pelagic larvae to benthic fossorial larvae in N. norvegicus as its onset can be influenced prevailing O-2 conditions, both in the laboratory and the field. (C) 2003 Elsevier B.V. All rights reserved.
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| 20. |
- Thor, Peter, 1965
(författare)
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Elevated respiration rates of the neritic copepod Acartia tonsa during recovery from starvation
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 283:1-2, s. 133-143
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Tidskriftsartikel (refereegranskat)abstract
- During prolonged periods of starvation, the respiration of copepods decreases to a basal metabolic rate. This is thought to enhance the survival probability by reducing the energy expenditure. The purpose of the present study was to investigate the recovery of the metabolism of Acartia tonsa from starvation. The respiration rate of nonstarved female A. tonsa was 0.95 +/- 0.17 nl O-2 individual(-1) min(-1) (mean S.E.). Starvation reduced the respiration rate to an average of 0.4 nl O-2 individual(-1) min(-1). Within a few hours after reintroduction to food, all starved individuals showed a hunger response in which their respiration rate not only increased to the respiration rate of those feeding constantly but also transiently rose above it. Thus, the maximal respiration rate of the starved individuals was 160% of the nonstarved rate. The duration of the hunger response depended on the duration of the preceding starvation period. The approximate amounts of oxygen respired in excess of the average nonstarved rate was 10 nl O-2 individual(-1) in copepods starved for 12 h, 60 nl O-2 individual(-1) in copepods starved for 24 h, and 150 nl O-2 individual(-1) in copepods starved for 36 h. The augmented respiration rates were probably induced to cover an increased energy demand for a "catch up" biosynthesis of gut cells and digestive enzymes during recovery. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 21. |
- Thor, Peter, 1965
(författare)
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Specific dynamic action and carbon incorporation in Calanus finmarchicus copepodites and females
- 2002
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 272:2, s. 159-169
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Tidskriftsartikel (refereegranskat)abstract
- Specific dynamic action (SDA) and incorporation of carbon into protein, lipids, and polysaccharides were measured in copepodite CV and adult female Calanus finmarchicus during the spring/summer growth season in Raunefjorden, Norway. Organic carbon from the food (Rhodomonas baltica) was allocated differently in the two developmental stages. Copepodites incorporated 50-80% of the carbon into lipids and only 7-22% into protein. Carbon incorporation into protein was higher in females, constituting 23% in May at 7 degreesC and 34% in June at 11degreesC. This resulted in significant differences in the magnitude of SDA, measured as the increase in oxygen consumption during and after an 8-h feeding event. On average, the rate of carbon incorporation into protein was 2 times higher and the magnitude of SDA was 2.5 times higher in females than in copepodites. There was a significant correlation between the magnitude of SDA and carbon incorporation into protein suggesting that SDA is linked to protein synthesis. When comparing ATP equivalents of the magnitude of SDA with ATP equivalents of the total amount of carbon incorporated. more energy was produced than consumed. This supports speculations of an energy demand associated with a rapid turnover of newly synthesised protein. (C) 2002 Elsevier Science B.V All rights reserved.
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| 22. |
- Wennhage, Håkan, 1965
(författare)
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Vulnerability of newly settled plaice (Pleuronectes platessa L.) to predation: effects of habitat structure and predator functional response
- 2002
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 269:2, s. 129-145
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Tidskriftsartikel (refereegranskat)abstract
- Plaice (Pleuronectes platessa) nursery grounds on the Swedish west coast have been subject to increasing cover of annual green macroalgae during recent years, with growth of algae starting at the time of plaice settlement in April to May. A laboratory experiment was performed to investigate how the vulnerability to predation of metamorphosing plaice was affected by the presence of filamentous algae. Predation by shrimps (Crangon crangon) on settling plaice larvae was higher on sand than among algae, whereas predation by crabs (Carcinus maenas) was unaffected by habitat type, suggesting a lower overall mortality of plaice in the vegetated habitat. When predators and prey were presented with a combination of the two habitats, predation by shrimps was as high as that in the sand treatment alone, whereas predation by crabs was lower than that in the two treatments with one habitat. Based on these results, an additional experiment was performed, investigating the functional response of shrimps to six densities of juvenile plaice in a sand habitat with alternative prey present. The proportional mortality of juvenile plaice (12 - 16 min total length (TL)) was density-dependent and was best described by a type III (sigmoid) functional response of the predatory shrimps. The results suggested that the combined predation pressure from shrimps and crabs was lower among algae than on sand, but settling plaice and predatory shrimps chose the sand habitat. Plaice densities in the sigmoid part of the obtained functional response curve represented normal to high field densities of plaice on the Swedish west coast, suggesting that shrimp predation could have a stabilising effect on plaice recruitment. The formation of macroalgae mats could therefore lead to a concentration of plaice juveniles in the remaining sand habitat and increased mortality through density-dependent predation by shrimps. (C) 2002 Elsevier Science B.V. All rights reserved.
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