Red Sea Symbioses
Population dynamics and metabolic interactions between giant sea anemones and?symbiotic anemonefish on Red Sea coral reefs
In the tropical Indo-Pacfic region, giant sea anemones and anemonefishes (clownfishes) form one of the most conspicuous and recognizable symbiotic interactions on coral reefs. The most abundant giant sea anemones on shallow reefs In the Red Sea, at the western edge of the Indo-Pacific, are bulb-tentacle anemones Entacmaea quadricolor and leathery anemones Heteractis crispa, where they host endemic two-banded anemonefish Amphiprion bicinctus. Our demographic analysis of these cnidarian populations in the Red Sea reveal the extent to which they are under stress, and are useful for assessment of how anthropogenic activities are currently disturbing coral reefs this region. In addition, both the anemones and clownfishes are heavily collected on some Indo-Pacific reefs for the ornamental aquarium trade, and better understanding of their demography is needed to develop a more sustainable fishery on these important organisms.
The population dynamics of fishes symbiotic with these cnidarians depend on those of their hosts, but little information is available across regions on patterns of population dynamics of the host cnidarians or the pomacentrid fish that associate symbiotically with them. In addition, physiological interactions may serve as a major mechanism of mutual influence on the demography of guest fishes and host cnidarians. Our group examines the impacts of resident fish on rates of oxygen consumption and production in zooxanthellate within the host cnidarians, and recently discovered that the characteristic “wiggle dance” of anemonefish serves to ventilate the host, especially at night when these large sea anemones may become hypoxic. We have also demonstrated that anemonefish influence nutrient transfer in this system, by producing ample inorganic nitrogen via their waste excretions to fertilize host anemones and influence their growth rates, but not enough phosphate for the uptake needs of the anemones.
The coral reefs of Jordan and Israel at the northern tip of the Red Sea support large populations of these organisms. For the past 20 years (since 1996), our group has been monitoring field populations of both the anemones and anemonefishes on reefs in Israel, as well as those in Jordan since 2008. Our work has involved NSF-funded training programs to expose American students to field survey methods and mathematical modeling techniques for analysis of population dynamics in the sea anemones, as well as assessment of respiration and photosynthesis in host sea anemones as affected by resident fish.
This continuing project increases understanding of the population dynamics of ecologically-important giant sea anemones and anemonefish, and their potential for recovery following disturbances on coral reefs. It also has revealed the extent to which the leathery sea anemone serves as nursery habitat for the fish. Our elucidation of how interaction among cnidarians and fish affects their patterns of oxygen and nutrient flux enhances understanding of the ways in which reef organisms are interconnected, and reveals the complexity of ecophysiological mechanisms in a coral reef symbiosis. This project also contributes to a scientific basis for the sustainable harvest of these organisms in other parts of the world where they are collected for the ornamental aquarium trade.
At Auburn University, we maintain long-term laboratory populations of both the sea anemones and their anemonefishes, which allow us to conduct manipulations to explore how aspects of the behavior, physiology, and reproduction of these organisms interact in this iconic symbiotic system.