Dr. Howard Lasker’s Research

Ecology of Caribbean octocorals: patterns of change, processes, and projections

Coral reefs are exposed to a diversity of natural and anthropogenic disturbances, and the consequences for ecosystem degradation have been widely publicized. However, the reported changes have been biased towards fishes and scleractinians, and there has been less attention to other taxa, the two most prominent such taxa on Caribbean reefs being octocorals and sponges. In a collaborative project with Dr. Peter Edmunds (Cal State, Northridge) I am working on an an “octocoral overlay” to the 25 y scleractinian-focused database that already exists for a series of sites on St. John, U.S. Virgin Is.

We are addressing this objective through analyses of benthic community structure in a National Park and Biosphere Reserve in St. John, where Edmunds has maintained one of the longest-running, long-term studies of coral reef community dynamics. This creates a unique opportunity to place octocoral ecology in a decadal context, and to exploit legacy data to better understand the present and immediate future. We are exploring temporal trends, and testing mechanisms driving community dynamics by repeating and extending existing species level surveys of octocoral abundance; conducting of manipulative and mensurative experiments focused on hypotheses addressing the selective advantage of octocorals versus scleractinians on contemporary reefs; and developing several types of ecological models to project octocoral and scleractinains community structure 5-25 y into the future.

Population ecology of Antillogorgia elisabethae

Antillogorgia elisabethae is a common gorgonian of coral reefs throughout the Caribbean. Colonies are harvested for pseudopterosin, a natural product that has anti-inflammatory properties and which is used as a topical agent in cosmetics. We are studying and modeling the population ecology of A. elisabethae focusing on those parameters crucial to the development of a management plan. The project encompasses studies of the species recruitment, growth and survivorship. We have also studied A. elisabethae population genetics as well as methods for colony propagation that can be used in mariculture. A larger and more general goal of the project is to identify the parameters that must be incorporated in analyses of coral populations and determine whether there are ”ecologic profiles” that can be used to differentiate species that should be highly protected from those for which managed harvesting is ecologically sound.

Evolution and development of colony form among gorgonian corals

Form affects the manner in which benthic taxa extract resources from the environment, resist physical disturbance and interact with competitors and predators. Understanding how form develops and varies within individuals over their life spans, between individuals across habitats and among species is a crucial component to understanding sessile taxa and their interactions with their environment and other biota. Using gorgonian corals as a model system I am conducting a multi-level analysis of colony form. The research focuses on models that address the question, “How are colonies organized?” Descriptive models along with a series of manipulative experiments are being used to determine which features of branches best characterize their future growth and branching behavior. Gorgonians like most colonial taxa have highly plastic colony forms. Is that plasticity produced by the local environment interacting with assembly rules that are themselves invariant or do assembly rules change as a function of the local environment and the colony’s history? These questions are being investigated using observational data and manipulative experiments.

Fertilization success among broadcast spawning benthic invertebrates

Analyses of marine invertebrate life history strategies have generally ignored fertilization rates as a factor in the organism’s life history, and most studies have implicitly assumed high fertilization rates. Our data (Lasker et al. 1996) on Caribbean gorgonians are among the few data on in situ fertilization rates for a broadcast spawning species. Fertilization rates of eggs vary from 0 to near 100% on different nights and different spawning events. The variance between sites and times is enormous, but much of the time many eggs go unfertilized. This result has now been verified in four different species on reefs in both Panama and the Florida Keys. The presence of sperm limitation among broadcast spawning species suggests a variety of reproductive strategies that may be pursued by colonies and also suggests dichotomies between male and female colonies. We are examining fertilization strategies among gorgonians using a combination of fertilization success models, data ib in situ fertilization and genetically determined paternity of larvae produced in natural spawning events.

Recent Grants

2013 – 2016

National Science Foundation – Collaborative Research: RUI-Ecology and functional biology of octocoral communities in St. John, USVI. (Collaborative with P. Edmunds, Cal State Northridge)

2008 – 2013

National Science Foundation – Collaborative Research: Recruitment dynamics and population connectivity in Bahamian octocorals (Collaborative project with C. Paris, University of Miami)

2007 – 2013

National Science Foundation – IGERT: Ecosystem restoration through interdisciplinary exchange (ERIE), PI, A. Rabideau, Co-PI with 3 other CoPIs

2006 – 2008

National Undersea Research Center, University of North Carolina at Wilmington. Recruitment dynamics of gorgonian corals – baseline recruitment and the effects of macroalgal cover.

2003 – 2008

National Science Foundation.  Recruitment among density manipulated populations of a Caribbean gorgonian.