Harbor Branch Oceanographic Institute

During the past two decades coral reefs in the greater Caribbean area have been altered by phase shifts away from corals and toward macroalgae or algal turfs. This study tested the hypothesis that because the phase shift on reefs in Jamaica and southeast Florida involved frondose macroalgae, bottom‐up control via nutrient enrichment must be a causal factor. The approach was multifaceted and included measurement of near‐bottom nutrient concentrations, salinity, nutrient enrichment bioassays, alkaline phosphatase assays, tissue C : N : P ratios, and tissue 15 N : 14 N ( δ 15 N) ratios. In both locations, concentrations of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) exceeded nutrient thresholds (∼1.0 µ M DIN, 0.1 µ M SRP) noted to sustain macroalgal blooms on Caribbean coral reefs. High seawater DIN : SRP ratios, alkaline phosphatase activity, and tissue C: P and N: P ratios of macroalgae on the carbonate‐rich Jamaican reef suggested SRP limitation of productivity compared to lower values of these variables on siliciclastic reefs in Florida that suggested DIN limitation. This pattern was corroborated experimentally when SRP enrichment increased P max (photosynthetic capacity at light saturation) of the chlorophyte Chaetomorpha linum in Jamaica compared to DIN enrichment that increased a (the photosynthetic efficiency under low irradiance) of the deeper growing chlorophyte Codium isthmocladum in southeast Florida. Increased DIN concentrations were associated with reduced salinity on both reefs, indicating submarine groundwater discharge was a significant source of DIN. Elevated δ 15 N values of C. isthmocladum tissue further pointed to wastewater DIN as a source of nitrogen contributing to the blooms in southeast Florida.

The biggest bloom Floating mats of Sargassum seaweed in the center of the North Atlantic were first reported by Christopher Columbus in the 15th century. These mats, although abundant, have until recently been limited and discontinuous. However, Wang et al. report that, since 2011, the mats have increased in density and aerial extent to generate a 8850-kilometer-long belt that extends from West Africa to the Caribbean Sea and Gulf of Mexico (see the Perspective by Gower and King). This represents the world's largest macroalgal bloom. Such recurrent blooms may become the new normal. Science , this issue p. 83 ; see also p. 27

Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all living vertebrates. Despite their dominant role in aquatic ecosystems, the evolutionary history and tempo of acanthomorph diversification is poorly understood. We investigate the pattern of lineage diversification in acanthomorphs by using a well-resolved time-calibrated phylogeny inferred from a nuclear gene supermatrix that includes 520 acanthomorph species and 37 fossil age constraints. This phylogeny provides resolution for what has been classically referred to as the “bush at the top” of the teleost tree, and indicates acanthomorphs originated in the Early Cretaceous. Paleontological evidence suggests acanthomorphs exhibit a pulse of morphological diversification following the end Cretaceous mass extinction; however, the role of this event on the accumulation of living acanthomorph diversity remains unclear. Lineage diversification rates through time exhibit no shifts associated with the end Cretaceous mass extinction, but there is a global decrease in lineage diversification rates 50 Ma that occurs during a period when morphological disparity among fossil acanthomorphs increases sharply. Analysis of clade-specific shifts in diversification rates reveal that the hyperdiversity of living acanthomorphs is highlighted by several rapidly radiating lineages including tunas, gobies, blennies, snailfishes, and Afro-American cichlids. These lineages with high diversification rates are not associated with a single habitat type, such as coral reefs, indicating there is no single explanation for the success of acanthomorphs, as exceptional bouts of diversification have occurred across a wide array of marine and freshwater habitats.

Computer-assisted structure analysis indicated (+)-discodermolide, a polyhydroxylated alkatetraene lactone marine natural product, was an antimitotic compound, and we confirmed this prediction. Previous work had shown an accumulation of discodermolide-treated cells in the G2/M portion of the cell cycle, and we have now found that discodermolide arrests Burkitt lymphoma cells in mitosis. Discodermolide-treated breast carcinoma cells displayed spectacular rearrangement of the microtubule cytoskeleton, including extensive microtubule bundling. Microtubule rearrangement that occurred with 10 nM discodermolide required 1 microM taxol. Discodermolide had equally impressive effects on tubulin assembly in vitro. Near-total polymerization occurred at 0 degree C with tubulin plus microtubule-associated proteins (MAPs) under conditions in which taxol at an identical concentration was inactive. Without MAPs and/or without GTP, tubulin assembly was also more vigorous with discodermolide than with taxol under every reaction condition examined. Discodermolide-induced polymer differed from taxol-induced polymer in that it was completely stable at 0 degree C in the presence of high concentrations of Ca2+. In a quantitative assay designed to select for agents more effective than taxol in inducing assembly, discodermolide had an EC50 value of 3.2 microM versus 23 microM for taxol.

Ocean color measured from satellites provides daily global, synoptic views of spectral waterleaving reflectances that can be used to generate estimates of marine inherent optical properties (IOPs). These reflectances, namely the ratio of spectral upwelled radiances to spectral downwelled irradiances, describe the light exiting a water mass that defines its color. IOPs are the spectral absorption and scattering characteristics of ocean water and its dissolved and particulate constituents. Because of their dependence on the concentration and composition of marine constituents, IOPs can be used to describe the contents of the upper ocean mixed layer. This information is critical to further our scientific understanding of biogeochemical oceanic processes, such as organic carbon production and export, phytoplankton dynamics, and responses to climatic disturbances. Given their importance, the international ocean color community has invested significant effort in improving the quality of satellite-derived IOP products, both regionally and globally. Recognizing the current influx of data products into the community and the need to improve current algorithms in anticipation of new satellite instruments (e.g., the global, hyperspectral spectroradiometer of the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission), we present a synopsis of the current state of the art in the retrieval of these core optical properties. Contemporary approaches for obtaining IOPs from satellite ocean color are reviewed and, for clarity, separated based their inversion methodology or the type of IOPs sought. Summaries of known uncertainties associated with each approach are provided, as well as common performance metrics used to evaluate them. We discuss current knowledge gaps and make recommendations for future investment for upcoming missions whose instrument characteristics diverge sufficiently from heritage and existing sensors to warrant reassessing current approaches.

Work on the life histories of common antarctic benthic marine invertebrates over the past several decades demands a revision of several widely held paradigms. First, contrary to expectations derived from work on temperate species, there is little or no evidence for temperature adaptation with respect to reproduction (gametogenesis), development, and growth. It remains to be determined whether the slow rates of these processes reflect some inherent inability to adapt to low temperatures, or are a response to features of the antarctic marine environment not directly related to low temperature, such as low food resources. Secondly, contrary to the widely accepted opinion designated as “Thorson's rule,” pelagic development is common in many groups of shallow-water marine invertebrates. In fact in some groups, such as asteroids,pelagic development is as prevalent in McMurdo Sound, the southern-most open-water marine environment in the world, as in central California. In other taxonomic groups, especially gastropods, there does seem to be a genuine trend toward non-pelagic development from tropical to antarctic latitudes. Although this trend has been predicted by theoretical models, its underlying causes appear to be group specific rather than general. Thirdly, pelagic lecithotrophic development, often considered to be of negligible importance, occurs in many shallow-water antarctic marine macroinvertebrates. Pelagic lecithotrophy may be an adaptation to a combination of poor food conditions in antarctic waters most of the year and slow rates of development. Nevertheless, some of the most abundant and widespread antarctic marine invertebrates have pelagic planktotrophic larvae that take very long times to complete development to metamorphosis. These species areparticularly prevalent in productive regions of shallow water (<30 m), which are frequently disturbed by anchor ice formation, and the production of numerous pelagic planktotrophic larvaemay represent a strategy for colonization. Although planktotrophic larvae tend to be seasonal in occurrence, their production is not linked particularly closely to the mid-summer pulse of phytoplankton production. These larvae show no evidence of starvation, even during times when phytoplankton abundance is very low, and they may depend on unusual sources of food, such as bacteria. How they escape the selective conditions that apparently led to a predominance of non-feeding modes of development in antarctic marine invertebrates remains as a major challenge for antarctic marine biology.

Trillions of plastic fragments are afloat at sea, yet they represent only 1-2% of the plastics entering the ocean annually. The fate of the missing plastic and its impact on marine life remains largely unknown. To address these unknowns, we irradiated post-consumer microplastics (polyethylene, PE; polypropylene, PP; and expanded polystyrene, EPS), standard PE, and plastic-fragments collected from the surface waters of the North Pacific Gyre under a solar simulator. We report that simulated sunlight can remove plastics from the sea surface. Simulated sunlight also fragmented, oxidized, and altered the color of the irradiated polymers. Dissolved organic carbon (DOC) is identified as a major byproduct of sunlight-driven plastic photodegradation. Rates of removal depended upon polymer chemistry with EPS degrading more rapidly than PP, and PE being the most photo-resistant polymer studied. The DOC released as most plastics photodegraded was readily utilized by marine bacteria. However, one sample of PE microplastics released organics or co-leachates that inhibited microbial growth. Thus, although sunlight may remove plastics from the ocean's surface, leachates formed during plastic photodegradation may have mixed impacts on ocean microbes and the food webs they support.

, were offered variously sized polystyrene microspheres (diameters 19-1000 μm) and nylon microfibers (lengths 75-1075 × diameter 30 μm), and the proportion of each rejected in pseudofeces and egested in feces was determined. For both species, the proportion of microspheres rejected increased from ca. 10-30% for the smallest spheres to 98% for the largest spheres. A higher proportion of the largest microsphere was rejected compared with the longest microfiber, but similar proportions of microfibers were ingested regardless of length. Differential egestion of MP also occurred. As a result of particle selection, the number and types of MP found in the bivalve gut will depend upon the physical characteristics of the particles. Thus, bivalves will be poor bioindicators of MP pollution in the environment, and it is advised that other marine species be explored.

Historic baselines are important in developing our understanding of ecosystems in the face of rapid global change. While a number of studies have sought to determine changes in extent of exploited habitats over historic timescales, few have quantified such changes prior to late twentieth century baselines. Here, we present, to our knowledge, the first ever large-scale quantitative assessment of the extent and biomass of marine habitat-forming species over a 100-year time frame. We examined records of wild native oyster abundance in the United States from a historic, yet already exploited, baseline between 1878 and 1935 (predominantly 1885-1915), and a current baseline between 1968 and 2010 (predominantly 2000-2010). We quantified the extent of oyster grounds in 39 estuaries historically and 51 estuaries from recent times. Data from 24 estuaries allowed comparison of historic to present extent and biomass. We found evidence for a 64 per cent decline in the spatial extent of oyster habitat and an 88 per cent decline in oyster biomass over time. The difference between these two numbers illustrates that current areal extent measures may be masking significant loss of habitat through degradation.

The discovery of abundant autotrophic macrophytes living below 200 meters indicates their importance to primary productivity, food webs, sedimentary processes, and as reef builders in clear oceanic waters. Estimates concerning minimum light levels for macroalgal photosynthesis and macrophytic contributions to the biology and geology of tropical insular and continental borderlands must now be revised.

Recent studies have shown that certain nocturnal insect and vertebrate species have true color vision under nocturnal illumination. Thus, their vision is potentially affected by changes in the spectral quality of twilight and nocturnal illumination, due to the presence or absence of the moon, artificial light pollution and other factors. We investigated this in the following manner. First we measured the spectral irradiance (from 300 to 700 nm) during the day, sunset, twilight, full moon, new moon, and in the presence of high levels of light pollution. The spectra were then converted to both human-based chromaticities and to relative quantum catches for the nocturnal hawkmoth Deilephila elpenor, which has color vision. The reflectance spectra of various flowers and leaves and the red hindwings of D. elpenor were also converted to chromaticities and relative quantum catches. Finally, the achromatic and chromatic contrasts (with and without von Kries color constancy) of the flowers and hindwings against a leaf background were determined under the various lighting environments. The twilight and nocturnal illuminants were substantially different from each other, resulting in significantly different contrasts. The addition of von Kries color constancy significantly reduced the effect of changing illuminants on chromatic contrast, suggesting that, even in this light-limited environment, the ability of color vision to provide reliable signals under changing illuminants may offset the concurrent threefold decrease in sensitivity and spatial resolution. Given this, color vision may be more common in crepuscular and nocturnal species than previously considered.

Marine aggregates incorporate particles from the environment, including microplastic (MP). The characteristics of MP in aggregates and the role of aggregates in linking MP with marine organisms, however, are poorly understood. To address these issues, we collected aggregates and blue mussels, Mytulis edulis, at Avery Point, CT, and analyzed samples with microspectrometers. Results indicate that over 70% of aggregates sampled harbored MP (1290 ± 1510 particles/m3). Fifteen polymer types were identified, with polypropylene, polyester and synthetic-cellulose accounting for 44.7%, 21.2% and 10.6%, respectively, of the total MP count. Over 90% of MP in aggregates were ≤1000 μm, suggesting that aggregations are a sink for this size fraction. Although size, shape, and chemical type of MP captured by mussels were representative of those found in aggregates, differences in the sizes of MP in pseudofeces, feces and digestive gland/gut were found, suggesting size-dependent particle ingestion. Over 40% of the MP particles were either rejected in pseudofeces or egested in feces. Our results are the first to identify a connection between field-collected marine aggregates and bivalves, and indicate that aggregates may play an important role in removing MP from the ocean surface and facilitating their transfer to marine food webs.

Reproductive cycles are determined from samples taken at regular intervals over a period of time related to the assumed periodicity of the breeding cycle. Fiscal, ship time and sampling constraints have made this almost impossible at deep-sea vents and seeps, but there is an accumulating mass of data that cast light on these processes. It is becoming apparent that most reproductive processes are phylogenetically conservative, even in extreme vent and seep habitats. Reproductive patterns of species occurring at vents and seeps are not dissimilar to those of species from the same phyla found in non-chemosynthetic environments. The demographic structure of most vent and seep animals is undescribed and the maximum ages and growth rates are not known. We know little about how the gametogenic cycle is initiated, though there is a growing body of data on the size at first reproduction. Gametogenic biology has been described from seasonal samples for only one organism from vent/seep environments. For other species, the pattern of gametogenesis has been described from serendipitous samples that allow determination of reproductive effort, but such samples reveal little about energy partitioning during the gametogenic process. Some notable adaptations have been described in mature gametes, including modified sperm. Spawning has been observed for a number of species both in situ and in vitro . Knowledge of the larvae of vent/seep organisms has been derived from laboratory fertilizations, from field collections over vent and seep areas and, for molluscs, from protoconch or prodissoconch size and shape. Larval dispersal has been perhaps the most intractable aspect of reproduction. Because the length of larval life is known for only a single seep organism and no vent organism, we cannot infer dispersal distance from a knowledge of current velocities. Modelling has been used to assess the maximum larval distance that allows effective migration between vent sectors. An indirect approach has been to estimate gene flow within, and between, vent sites using DNA sequencing and electrophoretic techniques. Although data are still equivocal, there are indications of considerable mixing among populations within and between vent sectors of the same ridge. Our knowledge of reproductive biology in vent and seep organisms remains fragmentary, but with molecular and biochemical techniques, emerging larval culture techniques, and increased sampling effort, the pieces of the jigsaw will eventually form an overall picture.

Ultraplankton, heterotrophic and autotrophic plankton c5 pm, are the most abundant food source in the world's oceans, yet their role as a food source for macroinvertebrates is largely unexamined. We quantified in situ feeding on heterotrophic and autotrophic plankton < l 0 pm by the boreal sponge Mycale l ~n g u a using measurements that quantified sponge feeding effic~enc~es, pumping rates, and abundance to determine the c o n t r ~b u t ~o n of plankton < l 0 pm to sponge carbon Intake. Using dualbeam flow cytometry we identified 5 populations of plankton c10 pm: heterotrophic bactena. Prochlorococcus, Synechococcus-type cyanobacteria, autotrophic eucaryotes <3 pm, and autotrophic eucaryotes 3 to 10 pm. Mycale lingua nonselectively grazed on all types of plankton < l 0 pm. Prochlorococcus was filtered with the highest efficiency (93%), followed by Synechococcus-type cyanobacteria (89%), autotrophic eucaryotes 3 to 10 I.lm (86":,), heterotrophic bacteria (74 %), and autotrophic eucaryotes c 3 pm (72%). We conservatively estimate that M. linqua at naturally occurring denslties can obtain 29 mg C d-' m-' feeding on plankton c10 pm, w ~t h 74% resulting from ultraplankton, suggestlng that ultraplankton are an important overlooked component of benthic-pelag~c coupling.

A new marine-derived macrolide designated as neopeltolide (1) has been isolated from a deep-water sponge of the family Neopeltidae. Its structure was elucidated on the basis of spectroscopic data interpretation. Neopeltolide (1) is a potent inhibitor of the in vitro proliferation of the A-549 human lung adenocarcinoma, the NCI-ADR-RES human ovarian sarcoma, and the P388 murine leukemia cell lines, with IC50's of 1.2, 5.1, and 0.56 nM, respectively. Neopeltolide (1) also inhibited the growth of the fungal pathogen Candida albicans with a minimum inhibitory concentration of 0.62 microg/mL.

Thalassia testudinum meadows from 0.5 m and 2.0 m (MLW) depths were studied a t 9 sites in the Florida Keys and western Caribbean. Two meadows, one offshore of a populated island with over 2000 septic tanks, and one offshore of a large bird rookery, were similar in having elevated levels of water column nutrients (DIN and SRP), greater epiphyte levels, low shoot densities, low leaf area indces, and low biomass. Increased blade turnover time was partially responsible for increased epiphyte levels offshore of the populated island, but epiphyte communities developed faster on seagrass blades there than at a paired site offshore of an uninhabited island. Results of aquarium experiments approximated the observed phenomena from the field studies: elevated water column nutrients produced increased epiphyte levels and decreased blade turnover rates. Reduced irradiance moderated the effect of nutrient enrichment on epiphyte levels. Elevated levels of water column nutrients, by stimulating epiphyte growth, reduced rhizome growth rates. This could b e related to the observed lower shoot density of T. testudinum meadows near sources of water column nutrient enrichment.

Biofouling causing an increase in plastic density and sinking is one of the hypotheses to account for the unexpectedly low amount of buoyant plastic debris encountered at the ocean surface. Field surveys show that polyethylene and polypropylene, the two most abundant buoyant plastics, both occur below the surface and in sediments, and experimental studies confirm that biofouling can cause both of these plastics to sink. However, studies quantifying the actual density of fouled plastics are rare, despite the fact that density will determine the transport and eventual fate of plastic in the ocean. Here we investigated the role of microbial biofilms in sinking of polyethylene microplastic and quantified the density changes natural biofouling communities cause in the coastal waters of the North Sea. Molecular data confirmed the variety of bacteria and eukaryotes (including animals and other multicellular organisms) colonizing the plastic over time. Fouling communities increased the density of plastic and caused sinking, and the plastic remained negatively buoyant even during the winter with lower growth rates. Relative surface area alone, however, did not predict whether a plastic piece sank. Due to patchy colonization, fragmentation of sinking pieces may result in smaller pieces regaining buoyancy and returning to the surface. Our results suggest that primarily multicellular organisms cause sinking of plastic pieces with surface area to volume ratios (SA:V) below 100 (generally pieces above a couple hundred micrometers in size), and that this is a "tipping point" at which microbial biofilms become the key players causing sinking of smaller pieces with higher SA:V ratios, including most fibers that are too small for larger (multicellular) organisms to colonize.

ABSTRACT Internal nitrogen pools in thalli of Gracilaria tikvahiae McLachlan were examined in three experiments as a function of total nitrogen content of the thallus, nitrogen deprivation, and nitrogen resupply. Amino acids and proteins appeared to form the major nitrogen storage pools in G. tikvahiae , while DNA appeared to be relatively unimportant in this regard. Inorganic nitrogen in the forms of NH 4 + and NO 3 − was found in the thalli; however, its contribution to the total nitrogen, pools was small. Within the protein pool, the phycoerythrin pigments appear important as a source of nitrogen when thalli are initially becoming nitrogen limited. In general, there was an inverse relationship between the levels of nitrogen and the carbohydrate content of the algal thalli.

Microcolin A [1] and microcolin B [2] are new immunosuppressive lipopeptides isolated from a Venezuelan sample of the blue-green alga Lyngbya majuscula. The microcolins are potent inhibitors of the murine mixed lymphocyte response and murine P-388 leukemia in vitro. Isolation and structure elucidation of 1 and 2 by nmr, mass spectral, and chemical methods are described.

Restoration of degraded ecosystems is an important societal goal, yet inadequate monitoring and the absence of clear performance metrics are common criticisms of many habitat restoration projects. Funding limitations can prevent adequate monitoring, but we suggest that the lack of accepted metrics to address the diversity of restoration objectives also presents a serious challenge to the monitoring of restoration projects. A working group with experience in designing and monitoring oyster reef projects was used to develop standardized monitoring metrics, units, and performance criteria that would allow for comparison among restoration sites and projects of various construction types. A set of four universal metrics (reef areal dimensions, reef height, oyster density, and oyster size–frequency distribution) and a set of three universal environmental variables (water temperature, salinity, and dissolved oxygen) are recommended to be monitored for all oyster habitat restoration projects regardless of their goal(s). In addition, restoration goal‐based metrics specific to four commonly cited ecosystem service‐based restoration goals are recommended, along with an optional set of seven supplemental ancillary metrics that could provide information useful to the interpretation of prerestoration and postrestoration monitoring data. Widespread adoption of a common set of metrics with standardized techniques and units to assess well‐defined goals not only allows practitioners to gauge the performance of their own projects but also allows for comparison among projects, which is both essential to the advancement of the field of oyster restoration and can provide new knowledge about the structure and ecological function of oyster reef ecosystems.