Characterizing Community Structure of Benthic Infauna From the Continental Slope of the Southern California Bight

Abstract

Infauna are an ecologically important component of marine benthic ecosystems and are the most common faunal assemblage used to assess habitat quality. Compared to the shallower waters of the continental shelf, less is known about the benthic fauna from the continental slope, especially how the communities are structured by natural gradients and anthropogenic stressors. The present study was conceived to rectify these data gaps and characterize the natural, baseline structure of the benthic infauna of the upper continental slope (200–100 m) of the Southern California Bight. We aggregated benthic infauna, sediment composition, and sediment chemistry data from different surveys across the Southern California Bight region (750 samples from 347 sites) collected between 1972 and 2016. We defined 208 samples to be in reference condition based upon sediment chemistry and proximity to known anthropogenic disturbances. Cluster analysis of the reference samples was used to identify distinct assemblages and the abiotic characteristics associated with each cluster were then used to define habitat characteristics for each assemblage. Three habitats were identified, delineated by geography, depth, and sediment composition. Across the habitats, there were detectable changes in community composition of the non-disturbed fauna through time. However, the uniqueness of the habitats was persistent, as the fauna from each habitat remained taxonomically distinct from irrespective of the decade of their collection. Within each habitat, subtle, assemblage-scale responses to disturbance could be detected, but no consistent patterns could be identified among the component taxa. As with the non-disturbed samples, there were compositional changes in the fauna of the disturbed samples through time. Despite the changes, fauna from disturbed and non-disturbed samples remained taxonomically distinct from each other within each decade of the dataset. After considering both the spatial and temporal patterns in the fauna of slope ecosystem, it became apparent that there was a high degree of stochasticity in the taxonomic organization of all three habitats. This would suggest that the benthic fauna from these communities may be neutrally organized, which in turn poses interesting challenges for future development of condition assessment tools based upon the benthic fauna in these habitats.

Zeta diversity patterns in metabarcoded lotic algal assemblages as a tool for bioassessment

“…Using models of how zeta diversity decays with sample order we found evidence of freshwater algal assemblages, both diatom and hybrid, tending to be assembled via a process of niche differentiation, which is in line with earlier studies (Dunck et al, 2021; Narwani et al, 2013; Pan et al, 1999; Passy & Legendre, 2006; Soininen, 2007), These results supported the use of zeta diversity in analyzing the ecology of freshwater algae, particularly with identifying likely processes of assembly. This is important in identifying the type of niche‐differentiated assemblages useful in constructing bioassessments, ranging from marine invertebrates (Gillett et al, 2021) to lichens (Nascimbene et al, 2013).…”

“…The use of zeta diversity can also help to investigate other questions relevant to the use of biological assemblages to track the effects of environmental changes, such as determining the relative likelihoods for different models of community assembly. Prior studies of groups of organisms used as biological indicators of anthropogenic activities have illustrated the importance of selecting assemblages that contain taxa with a diverse array of ecological niches and environmental sensitivities (Hilty & Merenlender, 2000; Resh, 2008; Simonin et al, 2019; Smol & Stoermer, 2010), with evidence also suggesting a process of niche differentiation being more likely than a stochastic one in such assemblages (Gillett et al, 2021; Passy & Legendre, 2006; Simons et al, 2019). The relative likelihood of these two models of community assembly, niche differentiation, and a stochastic process, can then be respectively calculated from the relative likelihoods of a power law and exponential decay models of how ζ N decays with N (Hui & McGeoch, 2014; McGeoch et al, 2019).…”

Initial estuarine response to the nutrient-rich Piney Point release into Tampa Bay, Florida

“…Additional monitoring and analysis are also required to fully understand the long-term impacts to bay resources beyond water quality. For benthic communities, sediments sampled in April and September near Port Manatee and surrounding waters suggested a mix of conditions dominated by "intermediate" and "healthy" benthic index scores (Wade et al, 2006, see https://shiny.tbep.org/piney-point), possibly reflecting the generally high spatial variability of macroinvertebrate communities in coastal habitats (Gillett et al, 2021;Karlen et al, 2020). Comparison of the April and September samples to historical conditions suggested relatively consistent benthic invertebrate community structure from 1993 to present (TBEP unpublished results).…”

Using Zeta Diversity in Describing the Health of Soft Sediment Benthic Macroinvertebrates in the Southern California Bight

“…The ability to infer the relative likelihood of these two processes of community organization is of relevance in developing bioassessments for BMI assemblages, with niche-differentiated assemblages having been found to be more reliable indicators of environmental conditions than stochastically ( i.e . neutral) organized assemblages (Gillett, Gilbane, and Schiff, 2021).…”

“…This study was designed to evaluate the utility of zeta diversity patterns of BMIs across the Southern California Bight (SCB) to determine: (1) The relative likelihood of niche vs. stochastic processes of community assembly in different coastal ecosystems; (2) Determining the reliability of zeta diversity-based models to account for variations in the regional biotic integrity of BMIs, and to account for how such models vary over both distance and environmental gradients; and (3) The minimum level of taxonomic sufficiency needed to meaningfully address question (2). The SCB was chosen as the study area given that it is a highly productive environment which experiences high levels of anthropogenic stress (Dodder et al ., 2016; Gillet et al ., 2021).…”