In situ measurements of seston uptake by constructed/restored oysterreefs in south Carolina

摘要

One of the metrics that can be used to assess the success of restored oyster reefs is their effect on water quality. This presentation describes a novel technique we have developed to provide rapid assessment of seston uptake (removal) by dense populations of bivalve molluscs, focusing on data gathered during May 2005 from five shellfish reefs of different ages, bivalve densities, and other characteristics in South Carolina. The overall technique involved concurrent sampling upstream and downstream of each study reef with in situ fluorometers and pumped water for laboratory analyses. In situ fluorometry detected significant differences between mean upstream and downstream readings for all five reefs, with total seston uptake ranging from 1.9% to 23.1%. Laboratory analysis of chlorophyll a concentrations in pumped water samples taken concurrently with the in situ fluorometry data showed substantial variability between upstream and downstream data, except for one reef which indicated an overall 35% uptake rate (compared to 23.1% based on in situ fluorometry data). As a control, sampling over recently constructed reefs (shell only) did not result in any measurable seston loss from the water column. Our system is a fast and effective approach to quantifying seston removal, and when data are logged at short-term intervals (seconds) potentially provides information on variations in feeding rates and related processes typically only available in laboratory studies.