National Marine Fisheries Service

About: National Marine Fisheries Service is a government organization based out in Silver Spring, Maryland, United States. It is known for research contribution in the topics: Population & Fisheries management. The organization has 3949 authors who have published 7053 publications receiving 305073 citations. The organization is also known as: NOAA Fisheries & NOAA National Marine Fisheries Service.

Effect of complexation by natural organic ligands on the toxicity of copper to a unicellular alga, Monochrysis lutheri1

Abstract: The effect of copper on the division rate of a unicellular alga, Monochrysis Zutheri, was tested in media with different concentrations of natural organic ligands. Filtered river water containing a high concentration of organic matter was added in different proportions to culture media to vary the level of copper complexation. Increased binding of copper by natural ligands was associated with decreased toxicity of a given concentration of added CuSO,+ The decrease in copper toxicity with increasing complexation could be explained quantitatively in terms of a dependency of toxicity on the concentration of free cupric ion. These results indicate that complexation of copper by organic ligands should considerably influence the toxicity of copper in natural waters through the effect of such complexation reactions on free cupric ion concentrations.

Feedback interactions between zinc and phytoplankton in seawater

Abstract: In Zn ion-buffered media, oceanic species (Thalassiosira oceanica and Emiliania hu.xZeyi) grew at near-maximal rates at the lowest free Zn ion concentration ((Zn2+) = lo- 12,3 M), whereas coastal species (Thalassiosira pseudonana and Thalassiosira weissflogii) were limited at (Zn2+) < lo-" M. The ability of the oceanic species to outgrow coastal ones at low (Zn2+) was due almost entirely to a reduced growth requirement for cellular Zn rather than to an increased capability for uptake. All isolates exhibited similar sigmoidal relationships between cellular Zn: C ratios and (Zn2+) with minimal slopes at (Zn2+) of lO-'o.5 to - 1 O-9.5 M and increasing slopes above and below this range. The minimal slopes at intermediate (Zr?+) could be explained by negative feedback regulation of a high-affinity Zn uptake system, while increased slopes at high (Zn2+) appeared to be related to uptake by a low-affinity site. Measured relationships between cellular Zn : C ratios and (Zn'+) agreed well with those computed from a modified Redfield model based on depth profiles for Zn and PO, concentrations and Zn chelation in the nutricline of the North Pacific. This agreement provides evidence that Zn concentrations in the nutricline are controlled by biological uptake and regen- eration as occurs for major nutrients.