Zooplankton of Southern California

Photographed and compiled by Peter J. Bryant (pjbryant@uci.edu)
Department of Developmental and Cell Biology, University of California, Irvine, CA 92697

Zooplankton (see the figure below) refers to the astonishing diversity of small animals that drift in the ocean, where they serve as the main consumers of phytoplankton as well as the main food source for a variety of secondary consumers including fish and whales. Zooplankton includes copepods, the most abundant metazoan taxon on earth. Studies of zooplankton provide a convenient and inexpensive method of marine habitat monitoring, giving an indication of the health of the phytoplankton population upon which these animals feed, as well as an indication of the levels of food availability for carnivorous animals higher in the food chain.

Some of the organisms in zooplankton (e.g. copepods) spend their entire life cycle in the water column, whereas others spend only the larval stages as plankton and then settle to the seabed, intertidal areas or other solid substrates for their adult stages. The larval stages show many important adaptations to pelagic life including filter-feeding mechanisms and appendages for maintaining position in the water column. The adaptations make the larval stages so different from the adults that special mechanisms of metamorphosis have evolved to allow the change from larva to adult (Hall and Wake, 1999; Hickman, 1999). This means that it is difficult to match larvae with corresponding adult stages by morphological analysis. However, species-specific DNA sequences can be used to make these correlations. We are exploring the diversity and abundance of zooplankton in Newport Bay, California, as well as the nearby Pacific Ocean, paying attention to geographic distribution as well as seasonality of the populations. We collect samples of zooplankton by pulling a net with a 150um mesh through a vertical or horizontal column of water. Individuals of each morphologically identifiable type are selected from each sample and recorded by photo- and video-microscopy, then preserved in ethanol for sequencing of the segment of mitochondrial DNA called the DNA Barcode. The samples are sent to the Barcode of Life (BOLD) consortium at the University of Guelph, Ontario, Canada for DNA sequencing.

DNA barcoding allows us to match up larval stages with the corresponding adults, which previously could be done only by the laborious rearing of individual larvae. DNA barcodes for many of the species we are studying have already been determined and made available by BOLD, so it is not always necessary to determine DNA barcodes for adults. The work includes all invertebrates that have pelagic stages of the life cycle, including crustaceans, annelids, mollusks, cnidarians, echinoderms and bryozoans.

Students will learn about techniques used in photomicroscopy and videomicroscopy by investigating zooplankton collected from various sites around Upper and Lower Newport Bay as well as from the open ocean. The project affords an excellent opportunity for students to learn many aspects of zoology and ecology that are not available through traditional classroom and laboratory work.

The work is covered by a Scientific Collecting Permit from the California Department of Fish and Wildlife.

References:

Barcode of Life: Identifying Species with DNA Barcoding. http://www.barcodeoflife.org/content/about/what-dna-barcoding. Accessed 11/4/2013

Hall, B. K. and Wake, M. V. (1999). Introduction: Larval Development, Evolution, and Ecology. pp 1-19 in: Hall, B. K. and Wake, M. V. (1999). The Origin and Evolution of Larval Forms. Academic Press, San Diego. 1999. 425 pp.

Hickman, C. S. (1999). Larvae in Invertebrate Development and Evolution. pp 21-59 in: Hall, B. K. and Wake, M. V. (1999). The Origin and Evolution of Larval Forms. Academic Press, San Diego. 1999. 425 pp.

Perry, R. (2003). A Guide to the Marine Plankton of Southern California. http://www.msc.ucla.edu/oceanglobe/pdf/guide_plankton1.pdf. Accessed 11/4/2013.

Young, C.M., Rice, M.E., and Sewell, M.A. (2002). Atlas of Marine Invertebrate Larvae. Academic Press, New York. 626 pp.