Landels-Hill Big Creek Reserve

20 Oct, 05 AM - 20 Oct, 07 AM

Marine macroalgae incorporate and adsorb various essential and non-essential elements. Essential elements, including trace metals, perform structural and metabolic roles in protein and sugar synthesis (DeBoer, 1981; Lobban and Harrison, 1994). Macroalgae of the genus Ulva are among the most common, cosmopolitan macroalgae found in coastal and estuarine ecosystems worldwide and are a food source for many invertebrates and fish. An increase in nitrate concentration has been shown to positively affect gross photosynthesis and chlorophyll content in Ulva rigida (Cabello-Pasini and Figueroa, 2005). Given the role that trace metals play in photosynthetic enzymes and proteins, variability in productivity could be driving the uptake of essential and non-essential elements. For my study I will test three hypotheses: 1) Trace element uptake (arsenic, cadmium, copper, lead, selenium, zinc, and mercury) by Ulva spp. will increase with increasing initial tissue nitrogen 2) Trace metal uptake (As, Cd, Cu, Pb, Se, Zn, Hg) by Ulva tissue with constant initial tissue nitrogen will increase with increasing ambient nitrate concentration, and 3) Herbivore (Idotea spp.) trace metal burden (As, Cd, Cu, Pb, Se, Zn, Hg) will increase with increasing metal burden in their diet. Ulva tissue will be sampled from 15-20 sites along the central California coast and analyzed for nitrate content. To test my first hypothesis, all samples will be exposed to standardized seawater with an added trace metal solution, under a range of light levels to determine the maximum metal uptake for each sample. I will test the second hypothesis by sampling from one site, then exposing those tissue samples to three ambient nitrate levels in mesocosms with standardized seawater and trace metals. I will carry out an analysis of covariance for both experiments, to determine if there is a relationship between either tissue nitrate and/or ambient nitrate and trace metal uptake. Finally, I will use Idotea spp. to test for trophic transfer of trace metals by Ulva spp. by feeding them algal tissue with varying trace metal content. I will compare their initial and final trace metal burden to determine if there is a relationship between their diet and their tissue metal concentrations. I predict that in Ulva spp., increased physiological function that accompanies nutrient enrichment (in tissues or in the environment) upregulates enzyme and protein production, requiring increased trace metal uptake. Additionally, I predict that some trace metals in this primary producer will be transferred to its grazers, such as Idotea spp. Few studies have been done that show a relationship between nitrogen and trace metals in algae, yet this is a crucial chemical relationship in polluted waterways. Specifically, there are no studies that look at maximum trace metal uptake as a function of photosynthesis. This study will help to create a predictive model of metal uptake by Ulva in relation to nitrogen, and thus contribute to water quality management decisions for both and ecosystem and human health.

Visit #23162 @Landels-Hill Big Creek Reserve

Approved

Under Project # 22650 | Research

Effects of tissue nitrogen and eutrophication on trace metal uptake and trophic transfer by Ulva spp.

graduate_student - California State University (CSU), Moss Landing Marine Laboratories

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Sonya Sankaran Oct 20, 2010 (1 days)

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Day use 1 Oct 20 (2 hours)
Day Use Only 1 Oct 20 (2 hours)