Variation in Seagrass-Associated Macroinvertebrate Communities Along the Gulf Coast of Peninsular Florida: An Exploration of Patterns and Ecological Consequences

Savanna C Barry,Thomas K Frazer,A Challen Hyman,Michal Kowalewski,Charles A Jacoby,Laura K Reynolds

doi:10.3389/fmars.2021.596966

Abstract

Seagrasses form vast meadows of structurally complex habitat that support faunal communities with greater numbers of species and individuals than nearby unstructured habitats. The Gulf coast of peninsular Florida represents a natural laboratory ideally suited to the study of processes that shape seagrass-associated invertebrate and fish communities within meadows of a single species of seagrass, Thalassia testudinum. This suitability arises from a pronounced structural and chemical gradient that exists over ecologically relevant spatial and temporal scales, as revealed by extensive monitoring of water quality and seagrass. We hypothesized that seagrass-associated invertebrate communities would vary across five estuarine systems spread along a spatial gradient in phosphorus concentration, an important driver of seagrass and phytoplankton growth in this region. The quantitative results based on data acquired at 25 stations (75 samples, 52,086 specimens, and 161 taxa) indicated that each of the five estuarine systems were distinct with regard to species composition and differences among systems were driven by abundant or relatively common species. In addition, we found evidence to indicate food webs in seagrass meadows along this gradient may differ, especially in the relative dominance of algal grazers and predatory invertebrates. These changes in species composition and trophic roles could be driven by phosphorus directly, through increases in rates of primary production with higher concentrations of phosphorus, or indirectly, through nutrient-mediated changes in the physical structure of the seagrass canopy. Our results suggest that differences in the habitat created by T. testudinum under differing phosphorus supplies lead to ecologically significant shifts in macroinvertebrate communities.

Highlights

Seagrasses are important structural components in shallow marine environments (Beck et al, 2001; Heck et al, 2003)
In all 75 samples, T. testudinum accounted for 71.4 ± 17.2% of the vegetative biomass and 91.6 ± 12.4% of the seagrass biomass
Differences in group dispersion cannot account for all of the significant effects found by PERMANOVA, and such variation was unlikely to be the major driver of the spatial differences in community composition, given the clear separation of groups on the non-metric multidimensional scaling (nMDS) plot (Figure 5A)

Summary

Introduction

Seagrasses are important structural components in shallow marine environments (Beck et al, 2001; Heck et al, 2003). Considerable uncertainty surrounds the response of faunal communities to other differences in vegetative structure, such as percent cover (Hovel et al, 2002; Gribben and Wright, 2014; McCloskey and Unsworth, 2015), the identity and diversity of seagrass species (Heck and Wetstone, 1977; Nelson, 1980; Jernakoff and Nielsen, 1998), and leaf height or shape (Bell and Westoby, 1986a; Schneider and Mann, 1991a,b; Edgar and Robertson, 1992). Despite decades of effort, relatively few generalizable relationships have emerged that link differences in seagrass-associated faunal communities with metrics of seagrass complexity, at spatial scales of kilometers or more (Boström et al, 2006), perhaps due to the challenges of finding suitable variation in environmental conditions and the complexity of meadows comprising one species of seagrass at such scales (e.g., Cardoso et al, 2007)

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Conclusion