Effects of Microbial and Heavy Metal Contaminants on Environmental/Ecological Health and Revitalization of Coastal Ecosystems in Delaware Bay

Abstract

The presence of heavy metals, excess nutrients, and microbial contaminants in aquatic systems of coastal Delaware has become a public concern as human population increases and land development continues. Delaware's coastal lagoons have been subjected to problems commonly shared by other coastal Mid-Atlantic states: turbidity, sedimentation, eutrophication, periodic hypoxic/anoxic conditions, toxic substances, and high bacterial levels. The cumulative impact of pollutants from run-off and point sources has degraded water quality, reduced the diversity and abundance of various fish species, invertebrates, and submerged aquatic vegetation. The effects are especially pronounced within the manmade dead end canal systems. In this article, we present selected case studies conducted in the Delaware Inland Bays. Due to the ecological services provided by bivalves, our studies in Delaware Inland Bays are geared toward oysters with special focus on the microbial loads followed by the water quality assessments of the bay. The relationships between oysters (Crassostrea virginica), microbial loads and nutrient levels in the water were investigated. The heavy metal levels monitored further away from the waste water treatment plant in the inland bays are marginally higher than the recommended EPA limits. Also, our studies confirmed that aerobic bacteria and Vibrionaceae levels are salinity dependent. Total bacteria in oysters increased when nitrate and total suspended solids increased in the waters. Studies such as these are important because every year millions of Americans consume raw oysters. Data collected over the last 10 years from our studies may be used to build a predictive index of conditions that are favorable for the proliferation of human pathogenic bacteria. Results from this study will benefit the local community by helping them understand the importance of oyster aquaculture and safe consumption of oysters while making them appreciate their ecological and commercial values. This will also be of tremendous help to the commercial shellfish aquaculture farms to predict poor conditions to prevent oysters' consumption when bacterial levels are high in water.

Effects of Contamination of Freshwater Habitat With Common Heavy Metals and Anions on the Prevalence of Human Adenoviruses and Enteroviruses

“…The higher levels at point A4 may be due to the proximity of the site to some agricultural activities along the strip. The concentration of phosphates has been correlated with agricultural practices involving the use of agro-based fertilizers in other studies ( 51 , 52 ). The higher concentration could also be attributed to runoffs from polluted industrial sections of the town to the lakefront.…”

Delaware Inland Bays and Market Oyster (Crassostrea virginica) Quality for Consumption

“…Our result is aligned with the study conducted by Chase et al [40] that the salinity (ranging from 1 to 35 ppt) was negatively correlated with V. vulnificus levels in water and sediments in their study. Ozbay et al [46] also found during the controlled laboratory experiment that oysters under low salinity treatments consistently yielded the highest total aerobic bacteria and Vibrionaceae levels. eir study confirms that high aerobic bacteria and Vibrionaceae levels are primarily salinity dependent.…”

The High Risk of Bivalve Farming in Coastal Areas With Heavy Metal Pollution and Antibiotic-Resistant Bacteria: A Chilean Perspective

“…The toxicity in the environment depends to a large extent on environmental conditions, as these influence the valence of the metal ions and thus their bioavailability ( Suvarapu and Baek, 2017 ). There is a growing understanding of the anthropogenic impact of metal contamination on the microbial community of aquatic ecosystems ( Ozbay et al., 2017 ; Yao et al., 2017 ; Igiri et al., 2018 ; Gillard et al., 2019 ; Rajeev et al., 2021 ; Liu et al., 2021 ).…”