During the November Aquarius mission, the last of 2001, several species of fish and a few other organisms will be captured, tagged, and tracked using two acoustic telemetry systems and conventional tagging strategies. The study has several goals related to understanding fish movements and their behavior in marine protected areas (MPAs). Understanding where fish move within and among reef sites and other habitats is fundamental to the design and implementation of MPAs, for the conservation of biological diversity, and fishery management.

A pilot project will also investigate how increased amounts of atmospheric carbon dioxide may affect coral growth rates. Seawater chemistry, specifically pH (adding carbon dioxide to seawater makes it more acid), can affect the ability of corals to produce their calcium carbonate skeletons. Global change is typically associated with increased seawater temperatures that are known to cause coral bleaching, but the carbon dioxide affects may be equally or more severe.

1. Fish tagging and behavior studies

The tagging projects are designed to track fish movements within Conch Reef, throughout the region, and over time. Conch Reef, located in the Florida Keys National Marine Sanctuary (FKNMS), was established as a Marine Protected Area in 1997, with no fishing or collecting allowed. Exceptions have been granted only for scientific research. Importantly, the Florida Keys include a network of 24 marine protected areas, from south of Miami to Key West, including approximately 150 square miles of the Dry Tortugas. While most of the protected areas are much smaller than the Tortugas Reserve, there is tremendous interest in understanding fish movements within and among protected sites, locally and regionally.

The simple premise, proven correct wherever implemented, is that no-take protection results in larger fish and greater numbers of fish - usually within five years but sometimes faster. However, it remains uncertain what effect these protected areas have on surrounding areas and fisheries. One essential piece of information is related to the movement of fish on a daily to seasonal basis, especially within the context of the network of marine protected areas that exist in south Florida.

Methods

Conventional and acoustic tagging techniques will be used during the mission to monitor the movements of fish, initially at Conch Reef and in the upper Florida Keys. Approximately 150 fish will be tagged using conventional external tags tested during a previous Aquarius mission. A tracking program is already in place including an established 800 number for reporting (in partnership with the National Marine Fisheries Service and Mote Marine Laboratory); program posters advertising the tagging program are distributed throughout the upper Keys and have been published in local newspapers. Tags are external (manufactured by Floy) and include a pennant with a coded letter, number, and color, so divers and snorkelers can report sightings without having to catch the fish. The pennants can be read from about 3 meters away by snorkelers and divers: fishers can read the 800 number directly of the plastic tag wire.

Additionally, two acoustic tagging programs will be implemented during the mission. A passive array of hydrophones will be deployed to record the presence and absence of fishes as they move throughout the Key Largo region. Five VR-1 acoustic receivers (VEMCO Limited LINK) will be deployed at Conch Reef at four pre-existing sites (NE Waystation, S-4 Site, and the Pinnacles mooring) and two additional moorings outside the Conch Reef protected area, to the northeast and southwest. The range of each receiver includes a radius of 400-500 m. Receivers will be placed by divers from the surface and will be anchored to the seafloor. A total of 20 fish (groupers and larger snappers) will tagged with V-8 acoustic pingers (VEMCO Limited), and subsequently released to the seafloor at the study site. Receivers will cycle every 1-minute for up to 120 days. Each V-8 transmitter will be coded to transmit a unique set of pings at 1-minute intervals for easy discrimination between tagged fish.

A second acoustic tracking program will be implemented directly from inside Aquarius. This work relies on hydrophones cabled to Aquarius that will be used to track species movements on a daily basis at Conch Reef. Candidate animals for this study include: spiny lobster (Panulirus argus), gray snapper (Lutjanus griseus), yellowtail snapper (Ocyurus chrysurus), nurse shark (Ginglymostoma cirratum), french angelfish (Pomacanthus paru), grey angelfish (Pomacanthus arcuatus), porcupinefish (Diodon hystrix), long-spined urchin (Diadema antillarum), and coney (Epinephelus
fulvus).

Fish and invertebrates will be tagged with acoustic tags manufactured by Lotek Engineering (Canada), who have agreed to be a partner in this project; they are only charging the program for their expendable items and staff time, loaning the hydrophone net and processing receiver for the project. The tagging procedure will be photographed and video taped. After tagging, the animals will be held for a recovery period and then released.

Each day divers will visually observe tagged animals while on excursions from Aquarius. The saturated divers will be able to stay with tagged animals for up to three hours at a time. Initial locations of tagged animals will be determined from inside Aquarius with the hydrophone array. Divers will then swim to that location with hand-held receivers that will enable pinpointing the animals while swimming, although due to the unique nature of the MAP_500 coding scheme individual tag identification will not be possible with the hand-held receivers. Visible fish tag markers will be used for this purpose.

During the Aquarius mission divers will visually observe tagged animals while on excursions from Aquarius. The saturated divers will be able to track and follow tagged animals during dives that can last three hours. Initial locations of tagged animals will be determined from inside Aquarius with the hydrophone array. Divers will then swim to that location with hand-held receivers that enable pinpointing of the animals while underwater. Behavioral observations will assess the condition of tagged animals and time spend in various habitats.

Results and applications

Results of the tagging studies help fulfill a recommendation made at a 1998 workshop that called for a demonstration project or "synoptic study" for electronic tags The specific recommendation was to: Select a location and target various animal groups to test the feasibility of simultaneously tagging several marine species and monitoring their movement and behavior relative to each other and to the oceanographic features of the region. This was envisaged as the best way to quickly advance the concept of using electronic marine animal tagging in a multi-disciplinary and comprehensive way, and could be a prelude to larger efforts in the future, perhaps covering entire ocean basins. Results will also be compared to work currently being conducted in the temperate northwest Atlantic (Stellwagen Bank National Marine Sanctuary) and to previous work in the Bahamas.

2. Coral growth rate studies

While much attention is currently focussed on the impacts of elevated sea-surface temperatures on reefs related to coral bleaching, the greatest impact of human-caused changes to atmospheric chemistry (increased concentration of carbon dioxide) may be on the ability of corals to produce their calcium carbonate skeletons. Reef-building corals must continuously deposit calcium carbonate, in the form of aragonite crystals, for growth, and to heal wounds inflicted by predators and physical disturbance. As a result, anything that compromises the rate of calcium carbonate production by corals can indirectly influence coral condition and mortality. Changes in atmospheric carbon dioxide can have this effect because the amount of carbon dioxide in seawater is directly influenced by atmospheric concentrations. As more atmospheric carbon dioxide dissolves in seawater the acidity of seawater increases, directly affecting the ability of corals to extract and deposit aragonite in their skeletons.

Methods

Small coral branch tips ("nubbins") from Madracis mirabilis (common name in Florida: yellow pencil coral) and small intact colonies of Porites astreoides (common name in Florida: mustard hill coral) will be used in experiments to directly measure coral calcification rates under different conditions of seawater chemistry that mimic past, present, and future atmospheric carbon dioxide conditions. The coral nubbins will be placed individually into special enclosed chamber devices outside Aquarius, adjacent to the web porch. Three experiments or treatments will be conducted that manipulate the seawater chemistry to monitor coral responses:

Treatment One: corresponding to an atmospheric carbon dioxide concentration equal to pre-Industrial Revolution conditions;

Treatment Two: ambient (no perturbation): equal to present day conditions; and

Treatment Three: corresponding to an atmospheric carbon dioxide concentration equal to projected levels by the end of the 21st Century.

Results and Application

Calcification rates measured during these experiments are expected to: remain unchanged in Treatment Two, the control (current levels); increase slightly for Treatment One (pre-industrial revolution levels); and drop from 10% to 50% in Treatment Three. The results will help validate current models related to calcification rates in corals and changes in seawater chemistry caused by changes in atmospheric carbon dioxide. It is well known that decreased calcification rates are not the only threat faced by corals (and other calcifying organisms). It is important, however, to quantify global stressors to coral reefs against the background of regional and local threats faced by reefs, such as pollution and over-fishing. Estimates and experimental data suggest that coral calcification rates may decrease nearly 40 percent in the next 50 years. It is also possible that calcification rates have already decreased substantially as a result of changing atmospheric and seawater carbon dioxide concentrations, which suggests that impacts may be much more severe than originally perceived.