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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Article
Student Research Papers, Fall 2012 (2012)

As secondary producers, zooplankton species are crucial as a vehicle for energy transfer in marine ecosystems worldwide yet few studies have observed the zooplankton community in tropical island estuaries. This study aims to understand the distribution of the zooplankton community in two of the largest estuaries (Opunohu and Cook’s Bays) in the volcanic tropical island of Moorea, French Polynesia. The results show that a few taxonomic groups, especially copepod, dominate the zooplankton composition. Moreover, the zooplankton community and diversity is highly variable at each bay and between bays. In the laboratory, copepod salinity response was examined. Copepods were placed at different salinity treatments for 16 hrs and dead copepods were counted. The salinity experiments show greater mortality of copepods at the extreme ends of salinity concentration, 40ppt and 0 ppt, suggesting that salinity is a major component influencing the abundance in these systems. Monitoring fluctuations in the zooplankton abundances will help understand changes in the marine food web as the result of climate change. 

    Cover page: ZOOPLANKTON ASSEMBLAGE IN OPUNOHU AND COOK’S BAYS (MOOREA, FRENCH POLYNESIA) AND THE RESPONSE OF COPEPODS TO CHANGES IN SALINITYCreative Commons 'BY' version 3.0 license
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2010)
    Mercury (Hg) stored in vegetation and soils is known to be released to the atmosphere during wildfires, increasing atmospheric stores and altering terrestrial budgets. Increased erosion and transport of sediments is well-documented in burned watersheds, both immediately post-fire and as the watershed recovers; however, understanding post-fire mobilization of soil Hg within burned watersheds remains elusive. The goal of the current study is to better understand the impact of wildfire on soil-bound Hg during the immediate post-fire period as well as during recovery, in order to assess the potential for sediment-driven transport to and within surface waters in burned watersheds. Soils were collected from three southern California watersheds of similar vegetation and soil characteristics that experienced wildfire. Sampling in one of these watersheds was extended for several seasons (1.5 years) in order to investigate temporal changes in soil Hg concentrations. Laboratory analysis included bulk soil total Hg concentrations and total organic carbon of burned and unburned samples. Soils were also fractionated into a subset of grain sizes with analysis of Hg on each fraction. Low Hg concentrations were observed in surface soils immediately post-fire. Accumulation of Hg coincident with moderate vegetative recovery was observed in the burned surface soils 1 year following the fire, and mobilization was also noted during the second winter (rainy) season. Hg concentrations were highest in the fine-grained fraction of unburned soils; however, in the burned soils, the distribution of soil-bound Hg was less influenced by grain size. The accelerated accumulation of Hg observed in the burned soils, along with the elevated risk of erosion, could result in increased delivery of organic- or particulate-bound Hg to surface waters in post-fire systems.
      Cover page: The Effect of Wildfire on Soil Mercury Concentrations in Southern California Watersheds
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