EFFECTS OF WIND-SPEED AND PARTICULATE MATTER SOURCE ON SURFACE MICROLAYER CHARACTERISTICS AND ENRICHMENT OF ORGANIC-MATTER IN SOUTHERN CHESAPEAKE BAY

Surface microlayer (SM) samples were collected with a rotating cylinde r sampler from the York and Elizabeth River estuaries of lower Chesape ake Bay bimonthly from May 1994 through June 1995. Two intensive sampl ings were also conducted in the York River during different seasons: o ne in December 1994 and another during June 1995. Four SM samples were collected during each intensive sampling within 4 days. All the sampl es were analyzed for total suspended particulates (TSP), particulate n itrogen (PN), particulate organic carbon (POC) and dissolved organic c arbon(DOC). The thickness of the SM was observed to decrease linearly with increased wind speed. TSP and POC in the SM were found to be enri ched up to 1000-fold over the corresponding subsurface water, and to b e exponentially related with wind speed at sampling. Enrichment of DOC in the SM relative to subsurface bulk water was also observed at both sampling sites. Larger average POC/PN ratios and consistently smaller particle sizes were observed in the Elizabeth River compared with the York River, suggesting that the former is heavily influenced try atmo spheric deposition, as well as urban and terrestrial runoff, whereas i n situ production of particles dominates in the latter. No seasonal tr ends were observed in the SM characteristics with the exception of par ticle size fractions in the York River, which fluctuate seasonally pre sumably due to changes in the dominant phytoplankton species. TSP and POC concentrations in the SM can be described by a first-order wind-dr iven mixing model. Wind-driven mixing of SM DOC was less apparent than for TSP and POC.