and four cumulative food webs from this study (NS, NB, PEI, Atlantic) depicted as temperate seagrass webs. the food web structure. Differences in food-web structure due to diversity changes can also affect the robustness of communities to species loss. During the day, we identified all sessile benthic and epiphytic fauna and flora as well as small, slow-moving, and cryptic macrofauna using 11 quadrats (50×50cm) placed every 5 m along the transect line. Although the proportion of epiphytes contributing to food webs did not change, these findings allude to the notion that greater surface area in seagrass meadows leads to higher availability of epiphytes, which in turn could support a larger community of animals. A) Study sites located in New Brunswick, Prince Edward Island, and Nova Scotia (see Table 1 for details). Not all energy is transferred from one trophic level to another. For each test, we first assessed skewness and individual correlations between food-web properties by constructing a draftsman plot (matrix of plots of each food-web property against the other), and examining the resulting Spearman rank correlations. The grey links represent feeding links. seagrass grazing in food web dynamics has been greatly underestimated in subtropical settings like the Florida Keys. Because the block effect was not significant, we then used a two-way fully crossed analysis comparing regions (NB, PEI) and impact levels (Low, Medium, High). We recommend further studies in seagrass meadows and adopting a common size‐based approach in order to generalize size spectra interpretations so that global seagrass research is enhanced and replicable across all locations (Duffy et al. The cumulative Atlantic seagrass food web had 107 trophic groups including 25 primary producers and detritus components, 36 invertebrate, 45 vertebrate groups, and an “import” group to account for import diets into the system (Methods S4). ), and bryozoans (e.g. Yes In Seychelles coral reefs, shallower slopes were found on more structurally simple reefs that were damaged by coral bleaching (Graham et al. Introduction. 2018 Jun;131(Pt A):468-480. doi: 10.1016/j.marpolbul.2018.04.046. S4, panel d), showed a clear change in contribution from epiphytes to seagrass in larger‐bodied animals; however, the contribution from benthic microalgae was not greatly affected by biomass. 1b). We analyzed abundance and body mass of individual animals using a maximum likelihood estimation (MLE) for the slope exponent, b, of the size spectra (Mb) and its associated standard error (SE; Edwards et al. PLoS ONE 6(7): Each point represents a study site within a Province (NB = New Brunswick, PEI = Prince Edward Island, NS = Nova Scotia) and impact level (Low, Medium, High). When species-specific information was not available, taxa were assigned to trophic groups composed of similar species according to ontogenetic stages (e.g. Some individuals were identified as outliers (smaller or larger than expected for this sampling method) and were excluded from analysis. Care and handling of all animals was in accordance with institutional guidelines. 2002), coastal seagrass meadows in Boston Harbor, USA (France et al. In NB, S, SWTL, MaxTL, and the trophic path length (Path) decreased from low to high eutrophication, while %I, the fraction of herbivore species (%H), and the generality (or number of prey per species, GenSD) increased. 2). In addition, to test for differences across blocks (4 levels, Fig. We present a detailed characterization of food webs associated with seagrass beds in different regions in Atlantic Canada, and show how these food webs change across a gradient of human impacts associated with eutrophication. Although seagrass communities have been well-studied in the field, a quantification of their food-web structure and functioning, and how these change across space and human impacts has been lacking. Seagrass animals were sampled using multiple tows of a beam trawl (2‐mm mesh) in each meadow (see Appendix S1: Table S4 for details). S4, panels c–d). Primary Consumers. Organisms in food webs are commonly divided into trophic levels. Body‐size distributions and size‐spectra: Universal indicators of ecological status? Efforts were made to sample and include as many organisms in the food web as possible with the aim of preventing bias towards higher trophic level organisms in our models. Thus, our results suggest that as seagrass food webs become more degraded they become more vulnerable to the loss of species that highly interact in the web. In addition, the comparison of some historical and more recent data highlights important declines of seagrass beds in several locations . https://doi.org/10.1371/journal.pone.0022591.g004. MDS ordination of cumulative food webs showed a clear distinction between regions (NB, PEI) (Fig. Within Atlantic Canada, seagrass food webs from low impact sites in NS, NB, and PEI showed similar food-web structure suggesting consistent features across local and regional scales, despite differences in localities (such as the connection to the open Atlantic Ocean in NS, open Gulf of St. Lawrence in PEI, and Northumberland Strait in NB) and food-web composition (Fig. This finding hints at the importance of epiphytes in seagrass food webs, regardless of habitat complexity. Overall, PEI webs were the least robust to species deletion, followed by NB and NS (Fig. There was a trend of declining %T in NB, and increasing %I and %H (but not %B) with increasing impact in both NB and PEI (as expected in Table 2). With increasing human impacts associated with eutrophication, however, food-web structure show evidence of degradation as indicated by fewer trophic groups, lower maximum trophic level of the highest top predator, fewer trophic links connecting top to basal species, higher fractions of herbivores and intermediate consumers, and higher number of prey per species. Were produced with FoodWeb3D, written by R.J. Williams, Pacific Ecoinformatics and Computational Ecology.. Of habitats is a national nature reserve and an important spawning ground in China seagrass shoots connected... A lack of larger animals in the Atlantic and regional webs trophic level to.... 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