Connectivity and Large Scale Ecological Processes

Connectivity Working Group

Connectivity refers to the interconnection of marine populations through larval dispersal, which in turn influence the dynamics of each population. At present there is very little information on levels of connectivity in coral reef regions, and management in Marine Protected Areas (MPA) depends too much on good luck and “guesstimates”.

Background

Marine populations are interconnected, exchanging individuals mainly through larval dispersal and thereby influencing the dynamics of each population.

Most reef species have pelagic larval stages. The dispersal during larval life means that neighbouring populations are connected by the exchange of larvae. This connection is termed “connectivity”.

Measuring connectivity is technically difficult for several reasons including: Long larval lines; Larvae is too small to be tagged; Its dispersal – a complex product of passive transport and active movement.

Many species are larval for many days or weeks and potentially able to travel large distances during this time. Their dispersal is strongly influenced by patterns of water movement, but larvae can sense their surroundings, respond to them and swim, sometimes surprisingly well. Larval behaviour also changes as the larvae develop and grow.

The movement of water around complex coral reef topography is itself far from simple.

Measuring connectivity requires field observations that are: Over large regions to encompass the potential extent of larval movement; Timed to coincide with critical biological events such as spawning pulses; and By people with a broad range of skills – physical oceanographers, ecologists, behavioural scientists and others.

It also benefits from use of sophisticated laboratory-based sciences including molecular genetics, trace element chemistry and advanced computer modelling. This is not routine monitoring.

Our Research

Research Activities

Until now, management of coral reefs, where it exists, has been reactive rather than proactive. With coral reefs entering a time of even greater stress, it is essential that managers develop more proactive management approaches, with a strong basis on science. Management of coral reefs, for conservation and/or for sustainable fisheries requires that we manage human impact to a level that is sustainable by the populations of reef organisms. This depends on the ability of the local (impacted) population to grow and population growth depends upon connectivity as well as on local reproductive potential. In particular, design and management of Marine Protected Areas depend on knowledge of the connectivity relationships of the local populations of targeted species.

The Connectivity research team is focusing on demographic connectivity (transfer of organisms). This is seen as the most challenging form of connectivity to investigate and studying demographic connectivity will inevitably require that we improve our capacity to model hydrodynamics that drive other forms of connectivity.

The primary objective of the Working Group is to undertake demonstration projects that will make empirical measurements of connectivity for selected species at specific locations. This means that new methods for tracing the movements of larvae from source populations to settlement sites will be developed. These new methods will become additional ecological tools for measuring demographic connectivity in other species and other sites, while the demonstration projects will provide early information on connectivity in the specific cases studied.

Research Update

The CRTR Connectivity Working Group aims to advance the science of connectivity and large-scale ecological processes and demonstrate its effectiveness for selected species in the Meso-American region. Key outcomes to June 2008 include:

Coral connectivity
Collecting coral tissue from juveniles, small adults and large adults across large sections of reefs in Belize and Mexico, the Group has characterised the genetic composition of these coral population. Genetic analysis has been based upon DNA extracted from the samples and is then used to assess if juveniles of a species have been produced by the local adult population. Tools to trace dispersal of planulae of Montastrea faveolata are being developed based on larval biology and behavior, immunogenetic probes to identify planulae, and magnetically attractive beads. The resulting data will then assist with development of reliable dispersal models of this species.

Post-settlement bottlenecks
To assess the bottlenecks in coral recruitment the Group is monitoring the settlement of corals at five sites in Meso-America, with permanent transects established at Belize, Guatemala, and Honduras. This forms the basis of large scale annual monitoring which is important as local marine populations are interconnected in a variety of ways, and the scale(s) of these interconnections must be taken into account if spatially explicit management programs are to be fully effective. The project is evaluating the demography of naturally occurring coral recruits and the factors affecting settlement. The project has already accumulated evidence that localised recruitment potential of reefs is a critical component of connectivity.

Connectivity in Bicolour damselfish
Research on bicolor damselfish is assessing several approaches to measuring connectivity in those reef species which do not aggregate over large distances to spawn. Sampling from Mexico to Honduras, the Group has made excellent progress combining genetic assignment tests, otolith microchemistry, ecology of settlement patterns, and hydrodynamic and habitat data to develop patterns of connectivity for populations of this common species.

Modelling lobster larval dispersal
The Group has obtained data from a rearing study on the longevity of the multiple larval stages of Caribbean Spiny Lobster (Panulirus argus) which will be critically important to the development of dispersal models for this species. Recruitment continues to be monitored to provide data for validating model output.

Capacity building and outreach
Much of the information on connectivity and recruitment data gathered in this research, and synthesised from other work, has supported training workshops for managers of reefs and protected areas. Members of local reef management communities have also been trained in monitoring procedures, in principle enabling data collection over a large area, but also providing these managers with feasible management strategies that they can implement at the local scale.

Who we are

Working Group Members

Working Group members bring international expertise and experience to this targeted research.

Project Partners

Working Group partners bring capacity to this research endeavour.

Contact

Connectivity and Large-Scale Ecological Processes Working Group:

Chair: Dr Peter F Sale
International Network on Water, Environment and Health, United Nations University

Co-chair: Dr Yvonne Sadovy
University of Hong Kong

Project Executing Agency: Global Coral Reef Targeted Research and Capacity Building for Management Program

C/o Centre for Marine Studies
The University of Queensland
Brisbane QLD 4072
Australia
Tel: +61 7 3346 9942
Fax: +61 7 3365 4755
Email:

Information Resources

Poster: CRTR Program Connectivity Working Group [download]
Brochure: CRTR Program Summary [download]
Research Update, July 2008 [download]
In 2007 the Oceanography Society published a special issue of Oceanography focussing on marine population connectivity. Two papers, including a major review, were co-authored by members of the CRTR Program's Connectivity Working Group.