Understanding the composition and structure of marine animal assemblages across space and time is essential in the establishment of effective management frameworks, particularly for holistic ...approaches to ecosystem conservation. Baited remote underwater video (BRUV) surveys are a well-established tool used in assessing relative abundances of marine fauna but are not commonly used in enclosed environments such as lakes. Sweetings Pond is an anchialine lake situated on the island of Eleuthera in The Bahamas that remains relatively undocumented, with only a single census available from 1983, yet has experienced an increase in stress from anthropogenic activity. Here, we investigated differences in community composition between sites and attempted to identify the species/benthic components driving changes using baited video surveys, before exploring differences in community structure between day-night periods. Nine species were identified over the 3780 min of BRUV footage analyzed, which was comparable to 1983 estimates. No difference in animal assemblages was seen between sites and no correlation with benthic composition was present. However, nocturnal replicates displayed higher median animal abundance and species richness than diurnal replicates, potentially resulting from a sequential food web aggregation around the light source. A number of unique, opportunistic feeding behaviors were also observed which opens avenues for future study. Overall, this study presents BRUVS as a viable and streamlined tool for managers of enclosed aquatic ecosystems to rapidly assess the system's macrofauna across day-night periods, supporting the requirements of an ecosystem-based management approach.
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•A single community is present within the Sweetings Pond anchialine ecosystem.•Nocturnal video surveys yield higher animal abundance and richness than diurnal.•Visual surveys appear inferior for larger animals (>5 cm length) compared to video.•Red light may act as a plankton aggregating device which then attracts predators.•This food chain effect is exploitable by surveyors of enclosed ecoystems.
The organic carbon (C
org
) stored in seagrass meadows is globally significant and could be relevant in strategies to mitigate increasing CO
2
concentration in the atmosphere. Most of that stored C
...org
is in the soils that underlie the seagrasses. We explored how seagrass and soil characteristics vary among seagrass meadows across the geographic range of turtlegrass (
Thalassia testudinum
) with a goal of illuminating the processes controlling soil organic carbon (C
org
) storage spanning 23° of latitude. Seagrass abundance (percent cover, biomass, and canopy height) varied by over an order of magnitude across sites, and we found high variability in soil characteristics, with C
org
ranging from 0.08 to 12.59% dry weight. Seagrass abundance was a good predictor of the C
org
stocks in surficial soils, and the relative importance of seagrass-derived soil C
org
increased as abundance increased. These relationships suggest that first-order estimates of surficial soil C
org
stocks can be made by measuring seagrass abundance and applying a linear transfer function. The relative availability of the nutrients N and P to support plant growth was also correlated with soil C
org
stocks. Stocks were lower at N-limited sites than at P-limited ones, but the importance of seagrass-derived organic matter to soil C
org
stocks was not a function of nutrient limitation status. This finding seemed at odds with our observation that labile standard substrates decomposed more slowly at N-limited than at P-limited sites, since even though decomposition rates were 55% lower at N-limited sites, less C
org
was accumulating in the soils. The dependence of C
org
stocks and decomposition rates on nutrient availability suggests that eutrophication is likely to exert a strong influence on carbon storage in seagrass meadows.
Climate change is altering the functioning of foundational ecosystems. While the direct effects of warming are expected to influence individual species, the indirect effects of warming on species ...interactions remain poorly understood. In marine systems, as tropical herbivores undergo poleward range expansion, they may change food web structure and alter the functioning of key habitats. While this process ('tropicalization') has been documented within declining kelp forests, we have a limited understanding of how this process might unfold across other systems. Here we use a network of sites spanning 23° of latitude to explore the effects of increased herbivory (simulated via leaf clipping) on the structure of a foundational marine plant (turtlegrass). By working across its geographic range, we also show how gradients in light, temperature and nutrients modified plant responses. We found that turtlegrass near its northern boundary was increasingly affected (reduced productivity) by herbivory and that this response was driven by latitudinal gradients in light (low insolation at high latitudes). By contrast, low-latitude meadows tolerated herbivory due to high insolation which enhanced plant carbohydrates. We show that as herbivores undergo range expansion, turtlegrass meadows at their northern limit display reduced resilience and may be under threat of ecological collapse.
This paper presents an analysis of the perception regarding reclaimed wastewater reuse in agriculture conducted in the European Union regions. The analysis is based upon a SWOT framework and applies ...a cluster analysis to reduce the dimension of the responses enabling an assessment of the different perceptions of water reuse. More than one hundred key actors identified among the regions participated in the evaluation of the relevance of aspects identified. The results indicate some groups of countries according to natural conditions (water scarcity) and the strategic role of agriculture as a key factor to determine agent’s perceptions and attitudes. The results indicate that the forthcoming EU regulation of water reuse should focus in the problems of the perceived high cost of reclaimed water for farmers and the sanitary risk perception for irrigated crops by consumers as the critical points for fostering the use of reclaimed water in agriculture and the need for regional implementation of the global regulatory framework.
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