Coral Ecosystem Connectivity 2013: From Pulley Ridge to the Florida Keys: Background: Mission Plan: NOAA Office of Ocean Exploration and Research

Mission Plan

Robert Cowen, Ph.D., Director and Project Lead - Hatfield Marine Science Center, Oregon State University
R/V F.G. Walton Smith: August 13-27, 2013
M/V Spree: August 19-29, 2013

This is the second year of a five year study to investigate the role that the mesophotic reefs of Pulley Ridge (off the southwest coast of Florida) may play in replenishing key fish species, such as grouper and snapper, and other organisms in the downstream reefs of the Florida Keys and Dry Tortugas (Figure 1). Mesophotic reefs are coral reef environments found at depths ranging from 30-40 m to greater than 100 m in the Gulf of Mexico where sufficient light enables certain reef-building corals (i.e. corals with symbiotic algae growing in them) to survive. Mesophotic reefs support a diversity of populations of algae, sponges, corals, other invertebrates and fishes.

Figure 1. Map of project area showing Pulley Ridge, off the west coast of Florida at depths of 200-330 feet in relation to the downstream reefs of the Dry Tortugas and Florida Keys. Colors represent water depth, which ranges from 33 feet (red) to depths of 820 feet or greater (dark blue). Current arrows depict prevalent current direction. Background image is from Google Earth and the depth information is from the U.S. Geological Survey and NOAA. Image courtesy of Robert Cowen. Download larger version (jpg, 1.4 MB).

In August 2013, we will be conducting our second year of fieldwork, using two separate vessels, the R/V F.G. Walton Smith (owned and operated by the University of Miami/RSMAS) from August 13-27 (Figure 2) and the M/V Spree (a charter dive vessel operated out of Key West, FL) from August 19-29. A total of 13 scientists and technicians will be on the Walton Smith and nine scientific divers and technicians will be on the Spree. Each vessel will address a different facet of the project.

Figure 2. The R/V F.G. Walton Smith, owned and operated by the University of Miami, Rosenstiel School of Marine and Atmospheric Sciences (RSMAS), is one of two vessels that we will be using during this expedition. Image courtesy of University of Miami/RSMAS. Download larger version (jpg, 723 KB).

On the Walton Smith, the science team will focus on:

Characterizing the benthic and fish communities using a surface driven remotely operated vehicle (or ROV). A high definition still frame camera, pointed downwards will record the abundance and distribution of benthic organisms and bottom type (e.g. sand, broken coral rubble, and live bottom). A video camera pointed forward will record fish species present and their abundance in front of the ROV as it moves along the bottom. By simultaneously recording the GPS position of the ROV, we can then estimate the area of the bottom actually covered and equate the abundance of the various organisms to density estimates.
Collecting genetic samples of larger fish species using fish traps. Some fish are too large and fast or too rare to adequately capture via the ROV cameras – this is especially true for the deeper groupers – and are more easily sampled using fish traps. Traps will be lowered to the bottom during the early evening and remain there throughout the night. At dawn, the traps are brought back up to shallower water where a diver will inspect each trap and if any grouper are present, the diver will deflate the fish’s swimbladder (to prevent damage to internal organs from changing pressure), then take length measurements and sample a small portion of the caudal fin for genetic studies.

Figure 3. A larval squirrelfish of the Family Holocentridae. Larval fish are sampled using plankton nets or light traps. Image courtesy of Cedric Guigand. Download larger version (jpg, 249 KB).

Characterize planktonic larval fish and invertebrates using plankton nets, imaging systems, and light traps. As we are interested in the dispersal potential of these various populations, we must pay particular attention to the larval (young) stages (Figure 3), since this stage is often where dispersal occurs – especially for species that remain closely affiliated with (or attached to) the bottom as adults. To achieve this, we sample the plankton (where the larval stages reside) using various nets, imaging systems and light traps – each method serves to capture information about different species. For example, we use plankton nets to catch the earliest stages of larval fish (post hatching to pre-settlement) whereas we use light traps to capture the larval fish as they end their larval stage and ‘settle’ to the bottom as juvenile fish. These specimens are also used for genetic studies and additional biological analyses (e.g. age and growth) back in the laboratory.

On the Spree, the science divers will be focused on collecting specimens of target taxa for population genetic analyses in the laboratory. We will make these collections in areas identified by the ROV surveys on the Walton Smith as supporting higher than average densities of the target species. All specimens will be used for genetic studies, and age and growth information for the fish species.