Abstract
Understanding the structure and function of infaunal communities is useful in determining the biodiversity and ecosystem function of shallow estuaries. We conducted a survey of infaunal communities within three separate water basins [Mosquito Lagoon (ML), Indian River (IR), and Banana River (BR)] in the larger Northern Indian River Lagoon, FL, United States to establish a database of infaunal community structure and function. Twenty-seven sites were sampled quarterly from 2014 to 2016. Analysis of all samples determined that basin, season, and sediment composition were the primary drivers of macrobenthic community composition. Diversity was highest in the ML, and lower in spring compared to other seasons. The occurrence of a brown tide (Aureoumbra lagunensis) in 2016 allowed a comparison of winter and spring communities before (2015) and during (2016) a bloom event. Community composition and diversity at the BR sites were the most affected by the bloom event with the lowest diversity and abundances during the bloom. Diversity in the IR was also lower during the bloom, while the ML was unaffected by the bloom. Species of all feeding groups were affected by the bloom, with lower abundances found in all groups. In addition, to determine the overall trophic diversity of infaunal communities, we collected infaunal organisms from two of the quarterly sampled sites for isotope analyses. Values of δ13C and δ15N from infaunal tissue were compared to those of potential food sources at each site. Substantial interspecific variation in isotope values of infaunal organisms within a site suggests the presence of diverse nutritional modes that include suspension and deposit feeding and predation. Together, these data suggest that infaunal communities contribute to benthic pelagic coupling and nutrient cycling within the estuarine communities, but the overall function of these communities may be tightly linked to their species composition.
Highlights
Biodiversity is an important component of resilient ecosystems at all levels
In 2014, diversity was lower in the Indian River (IR) and Banana River (BR) than the Mosquito Lagoon (ML) and did not differ between summer and fall samples (Table 1 and Figure 1A)
Disturbance plays a key role in community structure and function (Levin and Paine, 1974; Connell, 1978; Menge and Sutherland, 1987), with anthropogenic effects as a primary driver of disturbance in coastal systems (Hillebrand and Kunze, 2020)
Summary
Biodiversity is an important component of resilient ecosystems at all levels. From genetic to landscape, diverse communities promote healthy functioning and contribute to resiliency and survival in times of disturbance (Chapin et al, 2000). Soft sediment communities comprise a large portion of sea floor (Snelgrove, 1997, 1999; Ieno et al, 2006) and are composed of diverse taxonomic and functional groups with a wide array of feeding modes (Fauchald and Jumars, 1979; Snelgrove, 1999; Abreu et al, 2006; Galván et al, 2008) In addition to their critical role in nutrient and organic matter cycling, infauna are bioturbators that increase oxygenation of the sediments and affect sediment biogeochemistry through their movements (Snelgrove, 1999; Devereux et al, 2019). They are extremely good indicators of induced environmental changes
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