Marine allelochemicals generally are present in greater quantity and diversity in tropical than in temperate regions. Marine algal polyphenolics have been reported as an apparent exception to this biogeographic trend, with literature values for phenolic concentrations significantly higher in temperate than in tropical brown algae. In contrast, our results, the first reported for Caribbean brown algae (orders Dictyotales and Fucales), show that many species have high phenolic levels. In addition, both our study and previous studies with north temperate and tropical species demonstrate that there is marked variation in algal phenolic levels within species from different locations. We conclude that high phenolic concentrations occur in species from both temperate and tropical regions, indicating that latitude alone is not a reasonable predictor of plant phenolic concentrations.

The use of aquaculture systems to grow the seagrass Zostera marina (eelgrass) from seeds for restoration projects was evaluated through laboratory and mesocosm studies. Along the mid-Atlantic coast of North America Z. marina seeds are shed from late spring through early summer, but seeds typically do not begin to germinate until the late fall. Fall is the optimal season to plant both seeds and shoots in this region. We conducted studies to determine if Z. marina seeds can be induced to germinate in the summer and seedlings grown in mesocosms to a size sufficiently large enough for out-planting in the fall. Seeds in soil-less culture germinated in the summer when held at 14 • C, with percent germination increasing with lower salinities. Cold storage (4 • C) of seeds prior to planting in sediments enhanced germination and seedling survival. Growth rates of seedlings were significantly higher in nutrient enriched estuarine sediments. Results from preliminary studies were used in designing a large-scale culture project in which 15,000 shoots were grown and out-planted into the Potomac River estuary in the Chesapeake Bay and compared with an equal number of transplanted shoots. These studies demonstrate that growing Z. marina from seeds is an alternative approach to harvesting plants from donor beds when vegetative shoots are required for restoration projects.

The tropical brown alga Lobophora variegata (Lamouroux) Womersley has 3 distinct morphological forms (ruffled, decumbent and encrusting) along the Belizean barrier reef. These forms are commonly associated with habitats that differ in environmental characteristics and herbivore abundance. Previous research into among-habitat variation in plant susceptibility to herbivores has focused on interspecific comparisons; here we emphasize intraspecific variation. Field (fish) and laboratory (crab) experiments compared grazlng on L. vanegata forms with 2 other frondose algae of the same family (Dictyotaceae), the highly palatable Padina boergesenii and the unpalatable Stypopodium zonale. Transplant feeding studies were conducted in several reef habitats to determine if these forms differed in their susceptibility to fish herbivory. Significantly different susceptibilities to grazing among L. variegata forms for both fishes and crabs were observed. Preferences of fish and crabs were similar (from most to least preferred): Padina = ruffled Lobophora = encrusting Lobophora S decumbent Lobophora = Stypopodium. The distribution of ruffled and decumbent forms appears to b e related to the intensity of fish grazing normally encountered in their habitats and their differential susceptibility to herbivory. The encrusting form is common in areas with high fish and sea urchin herbivory, despite being susceptible to fish grazing when removed from the substrate. The presence of this form in areas of intense grazing pressure is probably related to its encrusting habit. We suggest that the distributions of these forms, their growth morphologies and potential defenses are in some measure related to differential grazing intensities among habitats. Form variation and habit may represent an important evolutionary strategy for tropical algae when herbivory is locally intense but patchy.

Eelgrass wasting disease, caused by the net-forming protist Labyrinthula zosterae, is suspected as the causative agent in the North Atlantic population declines of the temperate seagrass Zostera marina in the 1930s, as well as in more recent localized die-offs. During these declines, populations of eelgrass in low salinity areas were less likely to decline and quicker to recover. The goal of this study was to understand the relationships between eelgrass wasting disease and salinity, and how phenolic acids, putative plant defense compounds, varied with salinity and infection. We studied these relationships through mesocosm experiments in which eelgrass shoots were inoculated with L. zosterae under different salinity treatments (5, 10, 15, 25 and 40). We used lesion area as a measure of the degree of infection. Phenolic acids were separated and quantified with reversed phase HPLC. Three phenolic acids, rosmarinic, gallic and ferulic, were identified in leaf and rhizome tissue. Lesion area decreased with a decrease in salinity, and the concentration of phenolic acids increased with lesion area in inoculated leaves. Concentrations of phenolic acids were not good predictors of resistance to L. zosterae infection. Our study supports the hypothesis that observed decreases in eelgrass wasting disease in low salinity areas are due to the inhibition of L. zosterae at lower salinities.KEY WORDS: Eelgrass · Zostera marina · Wasting disease · Labyrinthula · Salinity · Phenolic acid Resale or republication not permitted without written consent of the publisher

The plant growth regulators jasmonic acid and methyl jasmonate (MeJA) have recently been identified in a variety of marine algae; however, their role in these organisms is currently unknown. Here we report that exposure to MeJA, during periods of tidal emergence causes the induction of polyphenolic chemical defenses (the phlorotannins) in two populations of the common rockweed Fucus vesiculosus (Linnaeus). Phlorotannin concentrations were up to 1.6 times higher in the growing apices of F. vesiculosus from both Avery Point (Connecticut, USA) and Roosevelt Inlet (Delaware, USA) within 10–14 days after a single brief exposure to airborne MeJA at concentrations ranging from 5.42 to 542 nM. The timing and magnitude of this induced increase in phlorotannin concentration are similar to that caused by real and simulated herbivory, raising the question of whether jasmonates, or their oxylipin relatives, are natural elements of antiherbivore responses in Fucus, as they are in vascular plants.