Food Web Structures and Mercury Exposure Pathway to Fish in Minamata Bay.

We analyzed total mercury content (THg) and carbon (δC) and nitrogen (δN) stable isotope ratios in fish, subtidal macrobenthos, and particulate organic matter (POM) as a proxy for pelagic phytoplankton and attached microalgae as a proxy for microphytobenthos to investigate the mercury exposure pathway in fish. For four seasons, samples of the above-mentioned organisms were collected on five occasions (July and October 2018 and January, April, and July 2019) in Minamata Bay. Isotope analysis showed that Minamata Bay food web structures were almost entirely fueled by microphytobenthos.

Estimation of production and sedimentation of cyanobacterial toxins (microcystin) based on nutrient budgets in the reservoir of Isahaya Bay, Japan.

The increasing eutrophication of freshwater and brackish habitats globally has led to a corresponding increase in the occurrence of harmful cyanobacterial blooms. Cyanobacteria can produce highly toxic substances such as microcystins (MCs) that affect the health of livestock, wildlife, and humans. The present study broaden the understanding of cyanobacteria ecology and MC dynamics in the field, focusing on the estimation of the production and sedimentation rates of MCs in a natural habitat.

Bioaccumulation Patterns of Perfluoroalkyl Acids in an Estuary of the Ariake Sea, Japan.

To evaluate the bioaccumulation potential of perfluoroalkyl acids (PFAAs) in an aquatic food web, we measured the concentrations of nine PFAAs in the water and aquatic organisms from an estuary of the Omuta River, Japan. Average log bioaccumulation factors for all PFAAs ranged from 2.0 to 2.

Widespread dispersal and bio-accumulation of toxic microcystins in benthic marine ecosystems.

Freshwater cyanobacteria produce toxic microcystins (MCs), which travel from freshwater areas into the sea. The MCs produced by cyanobacteria in a freshwater reservoir were discharged frequently into the adjacent Isahaya Bay, remained in the surface sediments, and then accumulated in various macrobenthic animals on the seafloor. The MCs were transported further outside of Isahaya Bay (Ariake Bay), and the median values of the MC contents in the sediments were in the same levels in both bays, while their temporal variations were also similar during the study period.

Short-term dynamics of cyanobacterial toxins (microcystins) following a discharge from a coastal reservoir in Isahaya Bay, Japan.

Freshwater cyanobacteria produce highly toxic substances such as microcystins (MCs), and water containing MCs is often discharged to downstream and coastal areas. We conducted field monitoring in Isahaya Bay to clarify the short-term dynamics of MCs discharged from a reservoir following a cyanobacteria bloom in the warm season. MCs were detected in the seawater of the bay (max.

Trophic magnification of polychlorinated biphenyls and polybrominated diphenyl ethers in an estuarine food web of the Ariake Sea, Japan.

To evaluate trophic biomagnification of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in an estuary of the Ariake Sea, Japan, we measured concentrations of 209 PCB congeners and 28 PBDE congeners, and nitrogen stable isotope (δ(15)N) levels in living aquatic organisms. The trophic magnification factor (TMF) for ΣPCBs (all 209 congeners) was 1.52, and TMFs for 58 PCB congeners ranged from 0.

Food sources for Ruditapes philippinarum in a coastal lagoon determined by mass balance and stable isotope approaches.

The relationship between the food demand of a clam population (Ruditapes philippinarum (Adams & Reeve 1850)) and the isotopic contributions of potential food sources (phytoplankton, benthic diatoms, and organic matter derived from the sediment surface, seagrass, and seaweeds) to the clam diet were investigated. In particular, we investigated the manner in which dense patches of clams with high secondary productivity are sustained in a coastal lagoon ecosystem (Hichirippu Lagoon) in Hokkaido, Japan. Clam feeding behavior should affect material circulation in this lagoon owing to their high secondary productivity (ca.