A Better Understanding of Coral Reef Ecosystems

Pelagic predators such as these barracuda, Sphyraena qenie, are part of the coral reef ecosystem in the U.S. Line Islands (NOAA Photo by Kevin Lino).
A team of scientists have embarked from Hawai'i on a three-month survey of coral reef ecosystems at Johnston Atoll, the U.S. Phoenix Islands, the islands of American Samoa, and the U.S. Line Islands in the tropical Pacific Ocean. The overarching objective is to better understand the coral reef ecosystems of these areas, many of which are seldom explored. The research expedition is part of a regular monitoring program, conducted by the Coral Reef Ecosystem Division (CRED), headquartered in Honolulu, Hawai'i. The expedition is supported by NOAA's Coral Reef Conservation Program and involves extensive cooperation among NOAA scientists and research partners, including the University of Hawaii Joint Institute for Marine and Atmospheric Research (JIMAR), the U.S. Fish and Wildlife Service, San Diego State University, and the Papahānaumaokuākea Marine National Monument.

The research expedition will be carried out from February 27 to May 24, 2012 aboard the NOAA ship Hi'ialakai. Under the leadership of Chief Scientists Dr. Jill Zamzow, Dr. Bernardo Vargas-Angél, and Jamison Gove, a diverse team of researchers will be conducting multidisciplinary coral reef ecosystem surveys, assessing the status of fishes, corals, algae, marine invertebrates, and the oceanographic conditions in which these organisms exist. The scientific data collected during the three-month research expedition will enable informed and effective implementation of ecosystem-based management and conservation strategies for coral reef ecosystems, helping to ensure their protection for generations to come.

Wednesday, May 9, 2012

Predator Dominated Reefs

By Brian Zgliczynski
Typical reef scene at Jarvis Island with large-bodied predatory species
patrolling the reef.
Upon entering the water, the fish team is typically greeted by numerous predatory fishes such as grey reef  sharks (Carcharhinus amblyrhynchos), twinspot snapper (Lutjanus bohar), black trevally (C. lugubris) , and coral grouper (Cephalopholis miniata). Large-bodied predatory species, which are common at Jarvis, are becoming increasingly rare throughout the tropical Pacific with fisheries exploitation exerting direct impact on reef-fish communities. Predatory species play an integral role in structuring coral reefs and the systematic removal of these important species can have detrimental impacts to the ecosystem.
Predatory species like jacks and sharks
are abundant at Jarvis

The fish team conducts surveys recording species composition as well as the number and size of all fishes observed in a predefined area. These data are converted into measures of abundance and biomass and used to estimate fish populations around an island or reef. At Jarvis, predatory species are highly abundant and account for over half of total fish biomass. Reef scenes like the one pictured above are commonplace. To put this into perspective, Jarvis has about 300 times more predatory fish biomass than the entire island of Oahu. The research conducted here has altered our perspective of the typical trophic pyramid in which predators (tertiary consumers) comprise a small fraction of total fish biomass in a reef ecosystem. At Jarvis Island, the trophic pyramid is inverted, with top predators accounting for a majority of fish biomass.
Trophic pyramids with species divided into their respective trophic categories.
Tertiary consumers = top-level predatory species, planktivores = species that
feed on microscopic organisms, Secondary consumers = lower-level carnivorous
species, and Primary consumers = herbivores. The Pyramid to the left represents
a degraded system with few predators (tertiary consumers) while the pyramid to
the right represents what researchers have observed at Jarvis Island,
where predators are highly abundant.
Grey reef shark, Jarvis.
As predator dominated coral reef ecosystems become increasingly rare in most parts of the world, contemporary ecological studies tend to concentrate efforts on systems that have already been degraded.  However, Jarvis Island represents one of the remaining examples of ecosystems in their natural state. Such systems provide an ecological baseline and an unprecedented opportunity for marine scientists to understand what ‘pristine’ coral reef ecosystems are like. A recently published article in the journal of Conservation Biology, Re-Creating Missing Population Baselines for Pacific Reef Sharks, is a great example of how the Coral Reef Ecosystem Division's monitoring program allows researchers to examine and compare the variations between these very different reef ecosystems across the Pacific. The article has gained national attention and was written up in Science Codex, by CNN, as well as the Washington Post.  It is studies such as this that support coral reef management and conservation efforts by providing the necessary science to aid in the development of effective ecosystem-based management and recovery plans towards the future.

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