Joel C. Creed

Disturbance and recovery of the macroflora of a seagrass (Halodule wrightii Ascherson) meadow in the Abrolhos Marine National Park, Brazil : an experimental evaluation of anchor damage

Anchor damage due to tourist visitation is becoming increasingly intense in the Abrolhos Marine National Park, Brazil, and is probably detrimental to the biota associated with the seagrass beds. In this study the effects of anchor damage on an algal dominated seagrass (Halodule wrightii) bed in the national park were measured and assessed. The mean size of anchor scars was 0.16 m2, and it was estimated that 0.5% of the seagrass beds were damaged per year by boat anchoring. The short term effect of simulated anchor damage (over 4 d) was a reduction in seagrass density, in the standing stock of Laurencia obtusa (Hudson) Lamouroux growing epiphytically on Udotea flabellum (Ellis and Solander) Lamouroux, and in the total macrophyte (seagrass + algae) standing stock. The longer-term (5, 9 and 13 month) ability of the seagrass and macroalgae to recover from damage, and possible seasonal differences in recovery ability, were determined. H. wrightii reoccupied experimentally cleared 0.25 m2 areas by vegetative elongation, and in 9 mo short shoot, rhizome and root biomass, and short shoot and rhizome densities were similar to controls. The ability of the seagrass to recover appeared not to be seasonal, and seasonality was only found in short shoot density. Recovering seagrass sent up more short shoots per length of rhizome than plants in undamaged areas. The most abundant macroalga was the rhizophytic Udotea flabellum; other algae grew on it as epiphytes or unattached. U. flabellum could recover quickly from simulated anchor damage, though other common algae (Dictyota mertensii (Martius) Kuetz., D. cervicornis Kutzing, Padina spp. and Laurencia obtusa) showed more complex patterns of recovery that were seasonally or species dependent. A perturbation such as an anchoring has an effect on the algal flora more than a year later, although most algae species and H. wrightii can recover more quickly. Notably large areas devoid of macrophytes within the seagrass bed may have been created by the fusion of anchor scars.

Quantification and Classification of Marine Litter on Beaches along Armação dos Búzios, Rio de Janeiro, Brazil

Abstract Anthropogenic debris constitutes a significant threat to the marine environment, representing a hazard not only for marine and terrestrial animals but also for human activities, health, and tourism. This study provided the first assessment of the type and quantity of marine litter at Armação dos Búzios, Brazil. Búzios is a popular tourist resort, which attracts visitors because of its proximity to Rio de Janeiro City. Sampling was conducted in belt transects of 4-m width, parallel to the coastline. To evaluate the composition and abundance of beach litter, all visible pieces of man-made debris (the number of items) found on each belt transect were identified in situ and recorded. Nearly 16,000 items of litter, belonging to seven categories were counted. An overall mean litter density of 13.76 items /100 m2 was quantified on the Armação dos Búzios beaches. Paper was the most abundant litter item, in particular, represented by cigarette butts. Much of the litter items are discarded by visitors to the beach. Nearshore, hard-bottom litter was also investigated at all beaches. Plastic was the most abundant submerged marine debris observed. Our results indicated that marine debris, particularly fishery-related debris (46% of marine litter) was most commonly found in the subtidal benthic environment. The abundance and distribution of litter through the Armação dos Búzios region seems to be especially influenced by recreational visitors, reflecting inadequate disposal practices.

Seagrass Ecosystem Services and Their Variability across Genera and Geographical Regions

Threats to and loss of seagrass ecosystems globally, impact not only natural resources but also the lives of people who directly or indirectly depend on these systems. Seagrass ecosystems play a multi-functional role in human well-being, e.g. food through fisheries, control of erosion and protection against floods. Quantifying these services reveals their contributions to human well-being and helps justify seagrass conservation. There has been no comprehensive assessment as to whether seagrass ecosystem services are perceived to vary over the globe or amongst genera. Our study compiles the most complete list of ecosystem services provided by seagrasses so far, including bioregional- and genus-specific information from expert opinion and published studies. Several seagrass ecosystem services vary considerably in their (known) provision across genera and over the globe. Seagrasses genera are clearly not all equal with regard to the ecosystem services they provide. As seagrass genera are not evenly distributed over all bioregions, the presence of an ecosystem service sometimes depends on the genera present. Larger sized seagrass genera (e.g. Posidonia, Enhalus) are perceived to provide more substantial and a wider variety of ecosystem services than smaller species (e.g. Halophila, Lepilaena). Nevertheless, smaller species provide important services. Our findings point out data gaps, provide new insight for more efficient management and recommend caution in economic valuation of seagrass services worldwide.

Intraspecific competition in Fucus serratus germlings: The interaction of light, nutrients and density

Abstract A factorial experiment investigated the effects of irradiance and nutrients on the growth and death of germlings of Fucus serratus (L.) cultured at different densities. Nutrient status, which consisted of nutrient enriched or normal filtered sea-water, was found to be the most important factor. Under high nutrient levels in culture plant growth was greatly stimulated, resulting in a more variable/unequal distribution of plant sizes in the population which tended to be positively skewed. Nutrients and density interacted to shape the mean plant size of these seaweeds; under low nutrients there was no difference between densities, but at high nutrient levels plants in low density populations were larger than in high density ones. However, survivorship was not only dependent on nutrients but also on density and light levels. Fewer plants survived in high density populations in high nutrient conditions, but high density populations grown under low nutrient conditions seemed to be more susceptible to the harmful effects of strong irradiance.

The invasion of the azooxanthellate coral Tubastraea (Scleractinia: Dendrophylliidae) throughout the world: history, pathways and vectors

In this review, we describe the history, pathways and vectors of the biological invasion of the azooxanthellate coral Tubastraea (Scleractinia: Dendrophylliidae) throughout the world. In order to do so we consulted previous reports in the literature and also compiled new unpublished information on the distribution of the three species of Tubastraea which have been reported as non indigenous species, both within their native and non-native ranges and also on vectors, and where cryptogenic. We combine these data with historical aspects of marine vectors in order to get insights into how Tubastraea species have successfully spread around the world, established and invaded and where future studies would be best focused. T. coccinea and T. tagusensis are recognized as being highly invasive and are causing significant environmental, economic, and social impacts requiring management actions. The third species, T. micranthus so far only reported outside its native range on oil platforms, may have similar potential for negative impact. The vectors of introduction of Tubastraea may have changed throughout history and the biological invasion of these invasive corals may reflect changing practices, demands and legislation in shipping activities over the years. Today it is clear that these corals are fouling organisms strongly associated with oil and gas platforms worldwide which are thus primary vectors for new introductions.

CHEMICAL COMPOSITION AND RELEASE IN SITU DUE TO INJURY OF THE INVASIVE CORAL Tubastraea (CNIDARIA, SCLERACTINIA)*

Defensive chemistry may be used against consumers and competitors by invasive species as a strategy for colonization and perpetuation in a new area. There are relatively few studies of negative chemical interactions between scleratinian corals. This study characterizes the secondary metabolites in the invasive corals Tubastraea tagusensis and T. coccinea and relates these to an in situ experiment using a submersible apparatus with Sep-Paks® cartridges to trap substances released by T. tagusensis directly from the sea-water. Colonies of Tubastraea spp were collected in Ilha Grande Bay, RJ, extracted with methanol (MeOH), and the extracts washed with hexane, dichloromethane (DCM) and methanol, and analyzed by GC/MS. Methyl stearate and methyl palmitate were the major components of the hexane and hexane:MeOH fractions, while cholesterol was the most abundant in the DCM and DCM:MeOH fractions from Tubastraea spp. The organic material retained in Sep-Paks® cartridges was tentatively identified as hydrocarbons. There was a significant difference between treatments and controls for 1-hexadecene, n-hexadecane and n-eicosane contents. The production of defensive substances by the invasive corals may be a threat to the benthic communities of the region, which include endemic species.

Do Small Seagrasses Enhance Density, Richness, and Diversity of Macrofauna?

Abstract Several studies have demonstrated that areas of seagrass show significantly greater density, richness, and diversity of fauna than adjacent unvegetated areas. Most investigations have dealt with midsized and larger seagrass species that usually form dense, highly structured meadows. Similar studies of smaller seagrasses have rarely been carried out. The objective of this study was to investigate whether the small, low biomass Halophila decipiens Ostenfeld confirms the paradigm observed in larger seagrass species by showing a greater macrofaunal density and diversity than adjacent bare, soft-bottom areas. Plant mean biomass at Urca inlet was 1.83 g m−2. Crustacea were the most abundant, frequent, and constant group in both habitats. Six taxa were significantly more abundant in the vegetated habitat, while only one taxon was enhanced in the habitat without H. decipiens. Total mean density, richness, and diversity of macrofauna were significantly higher in vegetated areas. Habitat complexity, higher productivity, or both associated with the seagrass were responsible for the differences found. Our results confirm and reinforce the paradigm that seagrass habitats have a greater density and diversity of macrofauna than adjacent unvegetated areas. However, adjacent unvegetated areas can present different sets of species that, even though less diverse, contribute to enhance local diversity.

Control of invasive marine invertebrates: an experimental evaluation of the use of low salinity for managing pest corals (Tubastraea spp.)

This study investigated the use of low salinity as a killing agent for the invasive pest corals Tubastraea coccinea and Tubastraea tagusensis (Dendrophylliidae). Experiments investigated the efficacy of different salinities, the effect of colony size on susceptibility and the influence of length of exposure. Experimental treatments of colonies were carried out in aquaria. Colonies were then fixed onto experimental plates and monitored in the field periodically over a period of four weeks. The killing effectiveness of low salinity depended on the test salinity and the target species, but was independent of colony size. Low salinity was fast acting and prejudicial to survival: discoloration, necrosis, fragmenting and sloughing, exposure of the skeleton and cover by biofoulers occurred post treatment. For T. tagusensis, 50% mortality (LC50) after three days occurred at eight practical salinity units (PSU); for T. coccinea the LC50 was 2 PSU. Exposure to freshwater for 45–120 min resulted in 100% mortality for T. tagusensis, but only the 120 min period was 100% effective in killing T. coccinea. Freshwater is now routinely used for the post-border management of Tubastraea spp. This study also provides insights as to how freshwater may be used as a routine biosecurity management tool when applied pre-border to shipping vectors potentially transporting non-indigenous marine biofouling species.

Perceptions of coral in a coastal tourist town in Brazil

Almost nothing is known about how non-scientists in coastal communities perceive corals. This study investigated public perception at a coastal town in Brazil. Individuals were asked to respond to specific questions concerning their knowledge, perception, and behaviour regarding corals. Although more interviewees believed they knew what the photograph of a gorgonian was, the stony coral pictures were identified correctly more frequently. Interviewees sometimes thought that the gorgonian was a plant, whereas stony corals were frequently identified as sponges, sea urchins or stones. Interviewees related the word “coral” to words such as alive, sea, plant, rock, animal, hurt, calcareous and jewellery. Moreover, interviewees intended to buy or collect corals no matter whether they knew what they were. This study revealed that people living, working and holidaying in a coastal town in Brazil have a poor understanding of corals.

Effect of phase shift from corals to Zoantharia on reef fish assemblages.

Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated.