Microplastics in four estuarine rivers in the Chesapeake Bay, U.S.A.

Once believed to degrade into simple compounds, increasing evidence suggests plastics entering the environment are mechanically, photochemically, and/or biologically degraded to the extent that they become imperceptible to the naked eye yet are not significantly reduced in total mass. Thus, more and smaller plastics particles, termed microplastics, reside in the environment and are now a contaminant category of concern. The current study tested the hypotheses that microplastics concentration would be higher in proximity to urban sources, and vary temporally in response to weather phenomena such as storm events. Triplicate surface water samples were collected approximately monthly between July and December 2011 from four estuarine tributaries within the Chesapeake Bay, U.S.A. using a manta net to capture appropriately sized microplastics (operationally defined as 0.3-5.0 mm). Selected sites have watersheds with broadly divergent land use characteristics (e.g., proportion urban/suburban, agricultural and/or forested) and wide ranging population densities. Microplastics were found in all but one of 60 samples, with concentrations ranging over 3 orders of magnitude (<1.0 to >560 g/km(2)). Concentrations demonstrated statistically significant positive correlations with population density and proportion of urban/suburban development within watersheds. The greatest microplastics concentrations also occurred at three of four sites shortly after major rain events.

Intersex (testicular oocytes) in largemouth bass (Micropterus salmoides) on the Delmarva Peninsula, USA.

The authors describe the prevalence and severity of intersex in the form of testicular oocytes in largemouth bass (Micropterus salmoides) collected over a 5-yr period from a variety of surface waters on the Delmarva Peninsula, USA, a region dominated by poultry production and agricultural land use. During a survey from 2005 to 2007 of approximately 200 male specimens representing 6 fish and 2 frog species collected from numerous small-order streams on Delmarva, intersex was observed in only largemouth bass (system-wide prevalence 17%). During 2008 and 2009, testicular oocytes were encountered in male largemouth bass from 6 lakes and 1 large river system, with prevalence ranging from 33% to 88% (weighted arithmetic mean, 57%). The prevalence of testicular oocytes in largemouth bass from Delmarva lakes was comparable to the highest levels reported in a national US Geological Survey reconnaissance of this species, which also occurred in regions of the Atlantic coastal plain with intensive row-crop and animal agriculture. To the authors' knowledge, the present study represents the first report in the peer-reviewed scientific literature of testicular oocytes in fish on the Delmarva Peninsula.