Research

Selected Research Articles 2001–Present
(Click here for selected research articles 1998–2000)

Below are abstracts of Rhode Island Sea Grant–funded research articles. To order a copy of the article, contact Rhode Island Sea Grant Communications at (401) 874-6842.

The National Sea Grant Library is the official Sea Grant archive. Library staff lend documents all over the world and maintain a searchable bibliographic database where you may obtain citations and abstracts of Sea Grant publications and, in many cases, a full text copy of the document.

Topics:
Coastal Ecosystems | Ecosystem Modeling | Eelgrass | Fishing Gear | Invasive Species | Lobster | Nutrients | Oyster | Salt Marshes| Summer Flounder | Ecolabeling

Coastal Ecosystems

• Nixon, S. W. 2003. Replacing the Nile: Are anthropogenic nutrients providing the fertility once brought to the Mediterranean by a great river? Ambio 32(1):30-39.
RIU-W-03-001 (P1653); 10pp.; $3.00.

The Nile River fertilized the Mediterranean Sea off the coast of Egypt until the high dam at Aswan was closed in 1965. Afterwards, the local fisheries collapsed, but began a dramatic recovery in the 1980s, coinciding with human population growth and development. Calculations indicate that human sewage and agricultural drainage may now support the fertility once provided by the Nile.

• Nixon, S.W. et al. 2004. A one-hundred-and-seventeen-year coastal water temperature record from Woods Hole, Massachusetts. Estuaries 27(3):397-404.
RIU-R-04-002 (P1704); 8 pp.; $3.00.

Near-surface water temperature measurements have been made almost daily at Great Harbor, Woods Hole, Mass., since 1886, perhaps the longest coherent sea surface temperature record in North America. Trends observed included cooling during the 1960s after no significant trend for the first 60 years of observation. Significant warming occurred from 1970 through 2002.

Ecosystem Modeling

• Brush, M.J. et al., 2002. Modeling phytoplankton production: Problems with the Eppley curve and an empirical alternative. Marine Ecology Progress Series 238:31-45.
RIU-R-02-004 (P1645); 15pp.; $3.00.

The discrepancy between measured and modeled rates of primary production, together with the importance of accurately predicting such rates, has led the authors to examine the traditional way in which phytoplankton growth and primary production are formulated in aquatic simulation models, and in particular the Eppley curve. The authors have searched the literature for evidence of culture studies that violate the curve, and have compared growth rates measured in situ to those predicted by the Eppley curve from two estuaries (Narragansett Bay, R.I., and Waquoit Bay, Mass.) and two mesocosm facilities at the University of Rhode Island. An empirical alternative to the Eppley curve is presented and examined for its potential application in estuarine simulation models.

• Sullivan, B. and C. Kincaid,. 2001. Modeling circulation and transport in Narragansett Bay. EOS Suppl. 82(2):S216.

Eelgrass

• Brush, M.J. and S.W. Nixon, 2002. Direct measurements of light attenuation by epiphytes on eelgrass Zostera marina. Marine Ecology Progress Series 238:73-79.
RIU-R-02-002 (P1640); 7pp.; $3.00.

Declines in the eelgrass Zostera marina in estuaries and lagoons have been attributed in part to reductions in irradiance reaching the grass blades. Epiphytes growing on Z. marina have the potential to attenuate a large fraction of the light that would otherwise reach the blades. In this study, scientists measured light penetration across a wide range of epiphytic densities by holding scraped and unscraped Z. marina blades over a submerged light sensor. Results indicate this method may be more accurate than those in previous studies.

• Harris, L.A. et al., 2004. Experimental studies of predation by bluefish Pomatomus saltatrix in varying densities of seagrass and macroalgae. Marine Ecology Progress Series 281:233-239.
RIU-R-04-003 (P1718); 7pp.; $3.00.

Researchers conducted ecosystem-level experiments to investigate predator-prey relationships in three habitat types: eelgrass Zostera marina, macroalgae, and bare sediment. Specially designed mesocosms containing marine sediments, coastal water, and varying densities of eelgrass or macroalgae were used to simulate conditions found in shallow coastal lagoons of Rhode Island. Bluefish were used as predators in each experiment. Eelgrass significantly increased the survivorship of silversides, tautog, and cunner at very low shoot densities. Experiments using macroalgae did not result in significantly different survival rates between bare sand and macroalgae habitat for silversides or cunner, the two species tested for this vegetation type.

• Nixon, S.W. et al., 2001. Responses of very shallow marine ecosystems to nutrient enrichment. Human and Ecological Risk Assessment 7(5):1457-1481.
RIU-R-01-005 (P1629); 25pp.; $3.00.

The authors have not been able to find useful relationships between nutrient input and the type of plant providing most of the primary production or between nutrient input and the amount of primary production in shallow lagoon ecosystems. However, total system production does increase with nutrient enrichment at very low rates of input, and eelgrass does not persist when exposed to even moderate levels of fertilization. Eelgrass responds to inorganic nitrogen enrichment and to shading by increasing the rate of leaf elongation and decreasing the allocation of resources to below-ground roots and rhizomes. This reduces or eliminates lateral branching of the rhizomes and causes a decline in the density of shoots. Based on mesocosm studies, the authors propose several indicators of eelgrass health, including the rate of leaf elongation, plant density, and the shoot:root biomass ratio.

Essential Fish Habitat

• DeLong, A.K. and J.S. Collie, 2004. Defining Essential Fish Habitat: A Model-Based Approach. Rhode Island Sea Grant, Narragansett, R.I. RIU-T-04-002 (P1695); 4 pp.

This booklet describes an improvement on the method of defining essential fish habitat that currently designates most of the species' range as "essential." This new approach can be used to obtain smooth and continuous regions representing any desired population percentile. Available as pdf.

Fishing Gear

• National Research Council, 2002. Effects of Trawling and Dredging on Seafloor Habitat. National Academy Press, Washington, D.C. 126pp.

Invasive Species

• Casagrande, R.S. 2003. Rhizedra lutosa, a natural enemy of Phragmites australis in North America. Estuaries 26(2B):602-606.
RIU-R-03-007 (P1697); 5pp; $3.00.

Rhizedra lutosa, an insect native to Europe and now found in North America, has been reported to cause serious damage to Phragmites australis in the Netherlands. Researchers are investigating the moth as part of an effort to characterize natural enemies of P. australis toward a goal of biological control of this invasive plant. They found that R. lutosa larvae feed on stems and rhizomes of P. australis growing in dry sites. They determined that the insect does cause a reduction of plant growth in some sites; however, because of low moth densities, this effect is small.

• Costa-Pierce, B.A. 2003. Rapid evolution of an established feral tilapia (Oreochromis spp.): The need to incorporate invasion science into regulatory structures. Biological Invasions 5: 71-74.

The hybridization of cultivated and native tilapia has made regulating exotic tilapia species difficult. This paper recommends that a system of ecotypes (code names) based on DNA markers be developed to label and regulate feral tilapia strains, and that hybrid strains be collected into a registry of species based on DNA markers.

Lobster

• Castro, K., et al. 2001. Habitat addition and stock enhancement for American lobsters, Homarus americanus. Marine and Freshwater Research 52(8):1253-1261.

Six experimental artificial reefs established in Narragansett Bay in 1997 have been monitored, and results show that juvenile and adult lobster density at the reef increased significantly compared with control areas. Settlement of young-of-year lobsters has significantly increased. The researchers used microwire tags to mark hatchery-reared lobsters and released over 2000 in each of two years. The density of young-of-year lobsters on enhanced reefs was not different from that on the control reefs. Only one hatchery-reared lobster was recovered. Field observations indicate possible behavior differences in hatchery-reared lobsters might make them more susceptible to predation.

• Saila, S.B. et al. 2002. Does lobster trap bait influence the Main inshore trap fishery? North American Journal of Fisheries Management 22: 602-605.

The purpose of this research is to determine whether evidence indicates that bait may make an important contribution to increases in lobster production.

Nutrients

• Buckley, B.A. and S.W. Nixon, 2002. A strikingly rich zone—Nutrient enrichment and secondary production in coastal marine ecosystems. Estuaries 25(4b):782-796.
RIU-R-02-003 (P1642); 15pp.; $3.00.

Unique multiple-year fertilization experiments were carried out over 50 years ago in Scottish sea lochs that showed dramatic increases in the abundance of benthic infauna and greatly enhanced growth of fish as a result of inorganic nitrogen (N) and phosphorus (P) additions. These experiments appear to provide a good qualitative model for the responses of the Baltic Sea to nutrient enrichment and resulting eutrophication. The authors review the literature for both locations. They also discuss the recent demonizing of N, and note that decisions regarding the amount of N or P that will be allowed to enter marine ecosystems should be made with the knowledge that there may be tradeoffs between increases in water clarity and dissolved oxygen and the abundance of fish, shellfish, and other desirable animals.

• McKenna, J.H. et al., 2001. Understanding groundwater nitrogen and carbon dynamics along estuarine margins: Insights and challenges. EOS Suppl. 82(2):S152.

• Nixon, Scott et al., 2001. Responses of very shallow marine ecosystems to nutrient enrichment.  Human and Ecological Risk Assessment, 7(5): 1457-1481, 2001.
RIU-R-01-005 (P1629); 25pp.

The authors have not been able to find useful relationships between nutrient input and the type of plant providing most of the primary production or between nutrient input and the amount of primary production in such shallow lagoon systems. However, total system production does increase with nutrient enrichment at very low rates of input, and eelgrass does not persist when exposed to even moderate levels of fertilization. "Zostera" responds to inorganic nitrogen enrichment and to shading by increasing the rate of leaf elongation and decreasing the allocation of resources to below ground roots and rhizomes. This reduces or eliminates lateral branching of the rhizomes and causes a decline in the density of shoots. Based on mesocosm studies, the authors propose several indicators of eelgrass health, including the rate of leaf elongation, plant density, and the shoot:root biomass ratio.

Oyster

• Munoz, P. and M. Gomez-Chiarri, 2002. Protease activity in the Eastern oyster, Crassostrea virginica, after experimental infection with the protozoan parasite Perkinsus marinus. J. Shellfish Res. 21(1):376.

Perkinsus marinus is responsible for disease and mortality of the American oyster, Crassostrea virginica. This study investigated the interactions between P. marinus and oyster hemocytes by measuring protease activity in plasma of oysters collected at intervals after experimental infection with P. marinus. This study provides insights into the role of proteases in the pathogenesis of Dermo disease.

Salt Marshes

• Bertness, M.D. et al., 2002. Anthropogenic modification of New England salt marsh landscapes. Proceedings of the National Academy of Science 9(3):1395-1398.

• Donnelly, J. and M.D. Bertness, 2001. Rapid shoreward encroachment of salt marsh vegetation in response to sea level rise. Proceedings of the National Academy of Science 98:14218-14223.

The distribution of New England salt marsh communities is intrinsically linked to the magnitude, frequency, and duration of tidal inundation. Cordgrass (Spartina alterniflora) exclusively inhabits the frequently flooded lower elevations, whereas a mosaic of marsh hay (Spartina patens), spike grass (Distichlis spicata), and black rush (Juncus gerardi) typically dominate higher elevations. This study examined relationships among marsh vegetation populations, climate warming, and sea-level rise.

• Emery, N.C. et al., 2001. Competition and salt-marsh plant zonation: Stress tolerators may be dominant comeptitors. Ecology 82(9):2471-2485.

Summer Flounder

• Gavlik, S. et al., 2002. Metamorphosis in summer flounder: Manipulation of thyroid status to synchronize settling behaviour, growth, and development. Aquaculture 203:359-373.

In the aquaculture of summer flounder, the inherent variation in growth and settling behavior during metamorphosis may lead to cannibalism and necessitate increased labor due to grading. The reasearchers' goal was to use thyroid hormone manipulation to synchronize settling behavior and produce uniform juvenile flounder. The treatment given eliminated the larger, potentially cannibalistic juveniles found in control tanks. Percent survival was unaffected by treatment.

Ecolabeling

• Johnston, R.J. et al., 2001. Measuring consumer preferences for ecolabeled seafood: An international comparison. Journal of Agricultural and Resource Economics 26(1): 20-39.

International seafood ecolabeling programs have been proposed to create market-based incentives for fisheries managers to promote sustainable fisheries. This study evaluates factors that may influence consumers' acceptance of such a program. Following a contingent-choice telephone survey of random households in the United States and Norway, a wide range of factors is found to influence consumers' likelihood of purchasing ecolabeled seafood, including price premium, species, consumer group, and certifying agency.