We present an extensive survey of floating plastic debris in the eastern North and South Pacific Oceans from more than 2500 plankton net tows conducted between 2001 and 2012. From these data we defined an accumulation zone (25 to 41 °N, 130 to 180 °W) in the North Pacific subtropical gyre that closely corresponds to centers of accumulation resulting from the convergence of ocean surface currents predicted by several oceanographic numerical models. Maximum plastic concentrations from individual surface net tows exceeded 10(6) pieces km(-2), with concentrations decreasing with increasing distance from the predicted center of accumulation. Outside the North Pacific subtropical gyre the median plastic concentration was 0 pieces km(-2). We were unable to detect a robust temporal trend in the data set, perhaps because of confounded spatial and temporal variability. Large spatiotemporal variability in plastic concentration causes order of magnitude differences in summary statistics calculated over short time periods or in limited geographic areas. Utilizing all available plankton net data collected in the eastern Pacific Ocean (17.4 °S to 61.0 °N; 85.0 to 180.0 °W) since 1999, we estimated a minimum of 21,290 t of floating microplastic.

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Substantial quantities of small plastic particles, termed “microplastic,” have been found in many areas of the world ocean, and have accumulated in particularly high densities on the surface of the subtropical gyres. While plastic debris has been documented on the surface of the North Pacific Subtropical Gyre (NPSG) since the early 1970s, the ecological implications remain poorly understood. Organisms associated with floating objects, termed the “rafting assemblage,” are an important component of the NPSG ecosystem. These objects are often dominated by abundant and fast-growing gooseneck barnacles (Lepas spp.), which predate on plankton and larval fishes at the sea surface. To assess the potential effects of microplastic on the rafting community, we examined the gastrointestinal tracts of 385 barnacles collected from the NPSG for evidence of plastic ingestion. We found that 33.5% of the barnacles had plastic particles present in their gastrointestinal tract, ranging from one plastic particle to a maximum of 30 particles. Particle ingestion was positively correlated to capitulum length, and no blockage of the stomach or intestines was observed. The majority of ingested plastic was polyethylene, with polypropylene and polystyrene also present. Our results suggest that barnacle ingestion of microplastic is relatively common, with unknown trophic impacts on the rafting community and the NPSG ecosystem.

The Sargassum Watch System processes satellite data and feeds results to a Web portal, giving decision makers timely information on seaweed location and warnings for potential beaching events.

[1] Recent satellite-derived observations linked global scale phytoplankton fluorescence variability with iron stress and hinted at photophysiological responses associated with changing light levels. These photocompensation reactions, the sum of photoacclimation and photoadaptation, were examined with climatological data for the Gulf of Maine. Significant seasonal variability was observed in the fluorescence quantum yield that was unrelated to patterns of biomass. Up to 89% of the variability in the fluorescence quantum yield was explained by a physiology-based photocompensation model. Spatial variability in seasonal patterns was associated with differing hydrodynamic regimes. This variability in the quantum yield demonstrates that satellite-based fluorescence is inappropriate for phytoplankton biomass determinations. More importantly, the work presented here provides the modeling foundation for fluorescence-based investigations of temporal and spatial variability in phytoplankton physiology associated with growth irradiance. These space-based physiological observations have the potential to decrease uncertainties in future ocean color derived primary productivity estimates.Citation: Morrison, J. R., and D. S. Goodwin (2010), Phytoplankton photocompensation from space-based fluorescence measurements, Geophys. Res. Lett., 37, L06603,