Benthic Filtering Reduces the Abundance of Primary Producers in the Bottom Water of an Open Sandy Beach System (Kashimanada Coast, Japan)

Abstract

The effect of benthic filtering by the upogebiid shrimp Austinogebia narutensis on the abundance of primary producers in the water column was investigated on a wave‐dominated nearshore zone in central Japan facing the Pacific Ocean. Chlorophyll a concentration in the bottom layer of the water column decreased significantly with increasing population density of A. narutensis, suggesting that shrimp feeding reduces the abundance of phototrophic microorganisms in the bottom layer. Because the upogebiid shrimp commonly occur in the nearshore zone of sandy beaches, similar effects of their benthic filtering as reported in this study can be expected in areas where the shrimp is as densely present.

Bottom‐associated phytoplankton bloom and its expansion in the Arctic Ocean

“…Note that the magnitude of a subsurface bloom in the natural environment may be associated with the underwater irradiance, nutrient concentration, initial phytoplankton abundance, and ammonium resource competition with non‐photosynthetic organisms, as well as grazing pressure from benthic organisms (Cloern, 1982; Lucas et al, 2018; Seike et al, 2020). In addition, currents can also influence bloom development.…”

Trophic segregation in a burrow: the stable carbon and nitrogen isotope ratios of the burrowing shrimp <i>Upogebia major</i> and its commensal bivalve <i>Cryptomya busoensis</i>

“…Filter-feeding benthic invertebrates are particularly important in seafloor ecosystems because they reduce the abundance of primary producers and alter the nutrient dynamics in the water column (Officer et al 1982, Newell 2004, Dʼ Andrea & DeWitt 2009, Seike et al 2020. The burrows produced by filter-feeding invertebrates also increase the biodiversity in a benthic ecosystem because they often harbor other small commensal invertebrates (Anker et al 2005, Dworschak et al 2012.…”

“…Upogebiid shrimps are a representative group of ecosystem engineers on tidal flats and shallow-marine sea bottoms that can feed by filtering suspended organic particles from overlying seawater that circulates through their burrows (Fig. 1C) (Dworschak 1981, 1987, Nickell & Atkinson 1995, Dworschak et al 2012, Seike et al 2020. The upogebiid shrimp irrigates the burrow with water, which is filtered during suspension feeding.…”

“…We therefore measured the stable carbon and nitrogen isotope ratios to compare the food sources of the burrow producer (U. major) and the burrow associate (C. busoensis). In addition, we measured population density of both species to discuss the trophic competition among them and the effect of their benthic feeding on the overlying water because filtering by a dense population of the upogebiid shrimp can reduce primary producers in a water column (Griffen et al 2004, Seike et al 2020. We also investigated the vertical distribution of the two species using a stratified sampling method to clarify where the burrow host and burrow associate filter seawater within the burrow complex.…”