LARVAL BIOLOGY & ECOLOGY OF MARINE BENTHIC INVERTEBRATES
Larvae comprise the least understood life-history stage of marine benthic invertebrates. We are investigating the factors that determine larval survival and development, such as temperature, salinity and dietary conditioning. During their period of development, larvae may disperse over a wide range of distances from the parental habitat where they are released. Factors that affect their range of dispersal include larval swimming behaviour and hydrodynamics (water currents). Swimming patterns, in turn, can be influenced by food patchiness or the presence of predators. We are examining the relative importance of these factors in larval dispersal in the laboratory, using the Dalhousie running seawater system (AQUATRON) and experimental systems of flow manipulation (e.g. experimental no flow columns, re-circulating flume, oscillating-grid tank etc).
LARVAL SUPPLY AND RECRUITMENT OF ALIEN MARINE BENTHIC INVERTEBRATES
We are examining factors that regulate the colonization patterns of two species of benthic invertebrates that are alien to the region but have been established recently in the shallow subtidal habitat off Nova Scotia : the green crab, Carcinus maenas (left), and the bryozoan, Membranipora membranacea (right). Both species can have pronounced ecological and economic impacts. The invasive success of the green crab, which is spreading northwards along both coasts of N. America , has grave economic implications, particularly in areas of bivalve aquaculture, because of its voracity as a predator. For example, this species is considered responsible for the near-demise of the soft-shell clam fishery in New England in the 1950s. Infestations by the alien bryozoan species have been associated with the most recent destruction of the kelp beds on the Atlantic coast of Nova Scotia , which are habitats that harbour commercially important species such as lobsters. Using experimental manipulations in the laboratory and field settings, my students and I are attempting to understand the mechanisms that determine larval survival, settlement and recruitment of these two species, as well as their interactions with native species.
DISPERSAL & COLONIZATION AT HYDROTHERMAL VENTS
AND OTHER DEEP-SEA HABITATS
Hydrothermal vents can be ephemeral, patchy environments that may experience frequent and intense disturbances (http://ridge2000.bio.psu.edu/). To colonize new vents, species that form the dense assemblages in these habitats must be able to disperse over great distances, detect suitable substrates for settlement and recruit successfully. We have been investigating patterns in larval supply and recruitment, and how they may be affected by factors such as the presence of adults and the chemical and physical environment, in several areas: the Endeavour Ridge, a pilot Marine Protected Area (http://www.pac.dfo-mpo.gc.ca/ oceans/ Endeavour/Endeavour_e.htm), located within the Canadian EEZ on the west coast of Vancouver Island; on Axial Seamount, located west of the Oregon coast (http://www.pmel.noaa.gov/vents); and on the Mariana Arc in the western Pacific (http://www.pmel.noaa.gov/vents/ring-of-fire.html).
A novel approach to studying deep-sea ecosystems is the use of cable observatories. An array of scientific instruments is deployed on a network of fibre optic cables that lie on the ocean floor. Scientists can communicate with these instruments continuously, and monitor significant events that occur on the ocean floor or trigger sampling remotely. One such network (NEPTUNE) is currently being launched on the Juan de Fuca plate in northeastern Pacific (http://www.neptunecanada.ca). As part of NEPTUNE, we will study patterns of larval abundance, supply and colonization along the bathymetric gradient in Barkley Canyon ,
and try to relate these to physical and biological processes in the water column.
ECOLOGY OF DEEP-WATER CORAL ECOSYSTEMS
Deep-water corals have been receiving increased attention from the
scientific community and the public in the last decade, mainly because they form distinctive habitats in the otherwise relatively homogeneous deep sea. They are generally found in areas with hard substrate and relatively strong currents. In 2001, I organized and led a benthic expedition on the Scotian Slope and Shelf that allowed quantitative sampling of these habitats for the first time in Canada, using a remotely operated vehicle (ROPOS: http://www.ropos.com). Our studies focus on the megafauna that are associated with these biological assemblages, and attempt to understand spatial patterns in the abundance of these organisms. Using modeling approaches, we try to identify significant factors that influence the presence of gorgonian corals and to predict areas of potentially suitable habitat.
FERTILIZATION ECOLOGY OF TROPICAL AND TEMPERATE SEASTARS
Oreaster reticulatus was a conspicuous inhabitant of sand bottoms and seagrass beds throughout the Caribbean , but has been dangerously decreasing in abundance because it is being fished as a curio. The probability of its recovery depends on the ability of this species to produce larvae that can successfully recruit into parental habitats. With Drs. Bob Scheibling (Dalhousie University) and Craig Young (Oregon Institute of Marine Biology), we assessed fertilization success (and thus the potential size of a larval pool) in this seastar, using field fertilization experiments in the Bahamas coupled with predictive mathematical models.
A related seastar (Protoreaster nodosus) is found in similar habitats as O. reticulatus, but in the Pacific Ocean. We are examining aspects of the fertilization ecology of this species, such as nearest neighbour distances, fertilization in the laboratory, and larval development, in Palau , through the Palau International Coral Reef Center (www.picrc.org).
In Nova Scotia , the seastar Asterias rubens is abundant in kelp beds in the shallow subtidal habitat. We are beginning a project on the fertilization ecology of this species, using experimental manipulations in the laboratory and in the field. Specifically, we will address the role of individual spawning behaviour in fertilization success.
NSERC (Discovery, Equipment, Research, Collaborative Research Opportunities, Ship time Allocation) http://www.nserc.ca
Canada Foundation for Innovation (New Opportunities, Innovation)
NOAA National Undersea Research Program