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P.L. Klerks

Publications and source records attributed to P.L. Klerks.

3 recordsLinked to original sources
USGS2007

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO 3 -extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp ( Sergio trilobata and Lepidophthalmus louisianensis ) averaged 33/m 2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO 3 -extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Florida↗
USGS2003

Effects of salinity, pH and temperature on the re-establishment of bioluminescence and copper or SDS toxicity in the marine dinoflagellate Pyrocystis lunula using bioluminescence as an endpoint

Pyrocystis lunula is a unicellular, marine, photoautotrophic, bioluminescent dinoflagellate. This organism is used in the Lumitox ?? bioassay with inhibition of bioluminescence re-establishment as the endpoint. Experiments determined if acute changes in pH, salinity, or temperature had an effect on the organisms' ability to re-establish bioluminescence, or on the bioassay's potential to detect sodium dodecyl sulfate (SDS) and copper toxicity. The re-establishment of bioluminescence itself was not very sensitive to changes in pH within the pH 6-10 range, though reducing pH from 8 to levels below 6 decreased this capacity. Increasing the pH had little effect on Cu or SDS toxicity, but decreasing the pH below 7 virtually eliminated the toxicity of either compound in the bioassay. Lowering the salinity from 33 to 27??? or less resulted in a substantial decrease in re-establishment of bioluminescence, while increasing the salinity to 43 or 48 ??? resulted in a small decline. Salinity had little influence on the bioassay's quantification of Cu toxicity, while the data showed a weak negative relationship between SDS toxicity and salinity. Re-establishment of bioluminescence showed a direct dependence on temperature, but only at 10??C did temperature have an obvious effect on the toxicity of Cu in this bioassay. ?? 2003 Elsevier Science Ltd. All rights reserved.

Environmental Pollution↗