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- Deyanova, Diana, et al.
(author)
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Contribution of seagrass plants to CO2 capture in a tropical seagrass meadow under experimental disturbance
- 2017
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:7
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Journal article (peer-reviewed)abstract
- Coastal vegetative habitats are known to be highly productive environments with a high ability to capture and store carbon. During disturbance this important function could be compromised as plant photosynthetic capacity, biomass, and/or growth are reduced. To evaluate effects of disturbance on CO2 capture in plants we performed a five-month manipulative experiment in a tropical seagrass (Thalassia hemprichii) meadow exposed to two intensity levels of shading and simulated grazing. We assessed CO2 capture potential (as net CO2 fixation) using areal productivity calculated from continuous measurements of diel photosynthetic rates, and estimates of plant morphology, biomass and productivity/respiration (P/R) ratios (from the literature). To better understand the plant capacity to coping with level of disturbance we also measured plant growth and resource allocation. We observed substantial reductions in seagrass areal productivity, biomass, and leaf area that together resulted in a negative daily carbon balance in the two shading treatments as well as in the high-intensity simulated grazing treatment. Additionally, based on the concentrations of soluble carbohydrates and starch in the rhizomes, we found that the main reserve sources for plant growth were reduced in all treatments except for the low-intensity simulated grazing treatment. If permanent, these combined adverse effects will reduce the plants' resilience and capacity to recover after disturbance. This might in turn have long-lasting and devastating effects on important ecosystem functions, including the carbon sequestration capacity of the seagrass system.
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| 2. |
- Hamisi, Mariam I., et al.
(author)
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Nutrient enrichment affects the seagrass Cymodocea serrulata and induces changes to its epiphytic cyanobacterial community
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Other publication (other academic/artistic)abstract
- To better understand how elevated water column nutrient levels affect the performance of the seagrass Cymodocea serrulata as well as the composition and density of its associated epiphytes, two sets of experiments were carried out where nutrient concentration were manipulated in a flow though system containing seagrasses. The photosynthetic performance, growth characteristics and nutrient content (N:P) were followed for C. serrulata. Simultaneously the biomass, species composition for the epiphytic cyanobacteria, in particular diazotrophs was monitored. The photosynthetic capacity of seagrasses decreased with increase in nutrient concentrations and exposure time. Nutrient contents of seagrass leaves and epiphytes decreased after nutrient addition. A higher diversity of both heterocystous and non-heterocystous cyanobacteria was observed in the experimental seagrasses as compared with natural field samples. Many of the cyanobacterial sequences retrieved represented uncultured and potentially novel diazotrophic phylotypes. Diel nitrogenase activity measurements verified the presence of a distinct proportion of diazotrophs, which was negatively affected by moderate nutrient levels. These results demonstrate that seagrasses were physiologically stressed by the increased nutrient level as revealed by low maximum quantum yields, although the effect was not instant. In contrast the epiphytes whose response was apparent during the short term exposure to moderate nutrient concentration which also promoted rapid change in their composition.
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