Discovery and Description of Two Benthic Communities - Poritidae and Pennatulidae

Grant Winners

Deans

Abstract

Two benthic cnidarian communities were discovered in July 2010 in the southwest Gulf of California. The primary purpose of this research is to obtain basic descriptive ecological data on each. Poritidae - Porites sverdrupi is a rare, endemic branching coral found as widely scattered colonies (<0.5 m2) on coarse sediments. Uniquely high densities (~50 colonies m-2) of this species occur in a near-shore cove of Isla Catalana. We propose to perform detailed mapping of this area, measurement of colony density and size, and assess population health (endosymbiont density, disease incidence, and predation threats). Underwater photo quadrats will document the location and size of each colony, quantified through CPCe software analysis. This novel baseline data set allows future documentation of community change. Recent severe declines in coral health punctuates the need to determine the status of this unique coral population. Pennatulidae - Sea pens are sessile, plume-shaped benthic cnidarians that inhabit sediment. No previous data had been collected on their distribution, abundance or size in the SW Gulf of California until our benthic surveys were performed in July 2010. Two species (Stylatula elongata and Ptilosarcus undulatus) were observed near Isla San Fransiscito and El Pardito, and basic population data were obtained. We propose to return to these locations and more completely assess their population distribution, behavior and community interactions. In particular predation and intraspecific interactions will be documented. Sea pens are part of the diet of Chelonia mydas, the endangered Green Sea Turtle, as well as many sea stars and nudibranchs, suggesting they are an important part of the marine food web. Submersible temperature recorders document the temperature regime of each community providing data on the environmental "master factor" of organism distribution. These activities will provide important information to park managers charged with the protection of these valuable natural resources.