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Invited Talk
Shipping as a vector for bioinvasions in the United States: past, present, and future
Ruiz GM*, PW Fofonoff, AW Miller, BP Stevs, AH Hines
Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, Maryland 21037 USA
*Email: ruizg@si.edu
Biological invasions in coastal ecosystems result from a variety of human activities, and the relative importance of different transfer mechanisms (vectors) varies in space and time. For the continental United States, commercial ships have been a dominant vector over the past several hundred years. Approximately 350 non-native marine species of invertebrates and algae are considered established in U.S. waters. Most of these invasions are attributed to shipping as a vector, and the relative contribution of shipping (to documented invasions) has increased greatly over time. These organisms were transferred primarily in ballast tanks and on the underwater surfaces (hulls) of ships. However, because many species have life-stages that can occur in either location, it is difficult to estimate the relative importance of ballast versus hull fouling. At present, the U.S. receives annually ~100,000 commercial ship visits to various ports around the country. Based on current ship-specific information, we estimated annually that (a) the underwater wetted surface area (WSA) associated with these arrivals is roughly 800 million m2 and (b) the discharge of ballast water is approximately 100 million m3. While numerous studies document the density and diversity of organisms transferred in ballast tanks, and also the effects of ballast water exchange as a management strategy to reduce such transfers, relatively few data exist to document biota on ships’ hulls. Several studies are underway to characterize biota associated with hulls and to begin exploring effects of various coatings on hull communities. Although management efforts are focusing intensively on reducing the quantity of organisms transferred on ships, and especially on ballast water discharge, the reduction in invasion risk is not well established and will depend upon (a) the shape of dose-response relationships between propagule supply and invasion establishment and (b) the relative importance of ballast versus hull fouling as a source of invasions. Advancing our understanding in these critical areas requires repeated, field-based measures to estimate temporal changes of invasion patterns in response to management as well as quantitative experiments to estimate establishment probability under diverse field conditions.
Keywords: Ships, Ballast water, Hull fouling, Invasions, United States
Larval development in Balanus amphitrite (Cirripedia:Thoracica): implications in biofouling and bioinvasion
Desai D*, AC Anil
National Institute of Oceanography, Dona Paula, Goa, India
*Email: ddattesh@nio.org
Most of the marine benthic/sessile organisms spend some part of their life in the water column (planktonic) as larva before they settle and recruit. Events during planktonic larval development have strong impact on settlement and recruitment success. Factors such as food concentration/starvation, temperature, salinity etc. influence the duration of larval development and also the ability of the larvae to metamorphose. The impact of these factors on larval development of an acorn barnacle Balanus amphitrite collected from a tropical estuarine environment was assessed.
Generally the larvae of B. amphitrite are raised in the laboratory through mono-species diatom culture e.g. Skeletonema costatum, Chaetoceros calcitrans, etc. The specific food availability in the nature and the concentration provided in the laboratory is far from reality. A comparison of the larvae raised in the microcosm in the field and that in the laboratory using mono-algal food indicated that the nutritional condition of the field reared larvae though inferior, was not comparable to the quantum of food assessed through chlorophyll a in the natural environment. This indicates the larvae are in a position to feed on other sources and complete development. Experiments on the starvation tolerance of these larvae showed that the ability to survive and undergo successful metamorphosis to be temperature dependent, i.e. 216h (5°C) to 48-60h (25°C). These results point out that these larvae are robust and capable of surviving under diverse stress conditions. In light of these observations it is possible for these organisms to endure the conditions inside the ballast tank. The presentation provides a basis for incorporating these factors of cirripede larval development into marine bioinvasion risk assessment.
Keywords: larval development, Balanus amphitrite, Food availability, Temperature, Marine bioinvasion Risk assessment
Susceptibility of phytoplankton to bioinvasion in a tropical, monsoon-influenced environment
D’Costa PM*, AC Anil
National Institute of Oceanography, Dona Paula, Goa, India
*Email: priya@nio.org
The phytoplankton community in a tropical port environment along the west coast of India was assessed for its susceptibility to bioinvasion. Since the South West (SW) monsoon is the main source of climatic variation in the study area, sampling was conducted during two consecutive post-monsoon periods (2001 and 2002) and the intervening pre-monsoon period (2002). Distinct seasonal trends in both – diatom and dinoflagellate communities were observed, with maximum values of species richness and diversity recorded during the pre-monsoon period. These observations indicate the potential for intra-seasonal variations in bioinvasion susceptibility. This presentation deals with the pre-monsoon and post-monsoon scenarios with respect to susceptibility of diatoms and dinoflagellates to bioinvasion and focuses on the strategies employed by these organisms to survive and compete under the circumstances. The effects of decadal changes in nutrient enrichment and variations in SW monsoon pattern on the phytoplankton community and its implications on ecosystem functioning are also elucidated.
Keywords: Diatoms, Dinoflagellates, Susceptibility, Bioinvasion, Pre-monsoon, Anthropogenic enrichment, South West monsoon
Invited Talk
Determination of benthic marine populations: from larval transport to survival to reproduction
Jesús Pineda*
Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
*Email:jpineda@whoi.edu
The population dynamics of coastal species such as barnacles, oysters and mussels are governed by many processes, including larval production, pelagic larval survival, larval transport, settlement and recruitment. These processes are complex, sequential, and some carryover to the next set of processes. For example, pelagic larval experience carries over to recruitment, and larval production determines how many larvae settle. Moreover, timing of each process may be critical to understand the “coupling” among processes and ultimately distribution and population dynamics of a species e.g. previous work has suggested that a mismatch in pelagic larval occurrence and phytoplankton algal blooms can result in recruitment failure.
In this talk I discuss (1) issues of timing, and (2) some of the complex phenomenology of the larval transport process. First, I discuss issues of timing at local scales (m’s) in the barnacle Semibalanus balanoides, a common barnacle in boreal rocky shores. In particular, I describe the recruitment window, the date vs. frequency function of the settlers that survive to reproduction. Our results suggest that the fine temporal scales of settlement rate (the rate at which free-living larvae attach to the bottom) can determine survival to reproduction. Second, I discuss some of the challenges and scales involved in investigating larval transport processes such as larval transport by internal tidal bores. Finally, I briefly discuss how focusing on the individuals that survive to reproduce (i.e. the recruitment window) may guide larval transport and dispersal studies, and reduce the number of variables and processes to a more manageable set.
Keywords: Benthic marine Populations, Larval transport, Semibalanus balanoides, Recruitment window, Survival, Reproduction
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