Coralliths are spherical, free-living (motile), scleractinian colonies inhabiting present day and ancient coral reefs. They form by the coral rolling on the seabed which can occur through biological and/or physical processes. While diving and snorkeling in nearshore environments in the upper Florida Keys, we observed hundreds of coralliths of varying sizes and species. This included colonies of Porites astreoides, Siderastrea radians, and Solenastrea bournoni . The largest coralliths we observed were all S. bournoni and ranged between 0.5 and 1.4 m in diameter. The exceptionally large colonies identified (>1 m) may be the largest and oldest spherical coralliths described to date. Relatively frequent movement of a corallith is key to their formation as all colony surfaces must be exposed to sunlight and currents periodically to maintain their spherical shape. Intuitively, the larger a corallith grows, the stronger the current energy must be to initiate movement. Considering the shallow depth of the corallith habitat and the high frequency of tropical storms and hurricanes impacting south Florida, we hypothesized that the forces generated by shoaling, breaking storm waves would be sufficient to cause the formation of these giant coralliths. Calculations based on hydrodynamic forces and field observations after the passage of a storm support the efficacy of storm-generated waves and surge to move and roll these giant coralliths. The tropical storm/hurricane return time where we found these large colonies in the Florida Keys is one in every seven years. This return time is apparently frequent enough to maintain their spherical morphology and assist in the formation of these giant coralliths.

The size, shape, and arrangement of tentacles in scleractinian coral polyps are likely to affect particle capture yet have not been investigated in a systematic way. Morphometric measurements of tentacles of several coral species found in the Caribbean Sea were taken from macro-photographs, and from these, models were constructed in three postures: straight, upstream-facing, and downstream-facing. These models were placed in a flume to video the flow paths of particles around them. Video analysis indicates tentacles, and their specific postures, have a dramatic effect on micro-flow patterns. The expanded soft tissue tentacles, and their specific postures, greatly increase probability of particle capture by direct impaction, inertial impaction, and gravitational deposition. All tentacle postures cause increased retention time relative to freestream travel in their immediate proximity, as well as increasing both contact with the tentacle surface, and tumbling of particles. Straight and upstream-facing tentacles deflect particles downward to their base, while downstream-facing tentacles deflect particles upwards. When results from individual tentacles are considered in geometric combination, the secondary radial symmetry of the tentacular whorls in simple coral polyps appears to be an optimal strategy to filter suspended particulate material in an oscillating and omni-directional flow environment. In meandrine corals, the hedgerows of straight and curved tentacles appear to draw particles downward, retain them, and direct them onto the oral feeding areas below the thecal ridges. The size, shape, and arrangement of tentacles are thus of key importance in understanding suspension feeding in scleractinian corals.

Coelentera are the largest components by volume in the gastrovascular system connecting polyps in a scleractinian colony. Thus to understand colony connectivity which is predicted to affect corals’ response to environmental change, we must first describe the dynamics inside these gastric cavities of individual polyps. We determined key time scales of mixing in coelentera by using microelectrodes to measure oxygen concentration after a light-to-dark transition in three polyps each of three colonies of Montastraea cavernosa in the laboratory. The gastrovascular system was modeled as an electrical network where voltage represents oxygen concentration, current represents oxygen flux, capacitors represent volume compartments, and resistors represent impedance to oxygen flux. The time constant of mixing, defined as the time needed for the system to disperse 63.2% of the fluid in the coelenteron, was determined from the oxygen dynamics in the coelenteron as modeled by a resistor-capacitor network. Time constants were on the order of three minutes and oxygen dynamics were well fit by the model prediction. However, as polyps depleted oxygen, we observed small magnitude (~ 0.1 ppm), high-frequency fluctuations in oxygen concentration. A power spectral density analysis identified two time scales of high-frequency mixing in the coelenteron. The greatest variance occurred at a period of 48.3 ± 2.8 seconds, with a secondary peak seen at 35.9 ± 2.3 seconds. The microenvironment within polyps of M. cavernosa can respond as fast or faster than their external environment can fluctuate, thus scleractinian polyps have the capacity to mediate their response to changing environmental conditions.### Competing Interest StatementThe authors have declared no competing interest.

Increasing ocean temperatures have widespread consequences for coral reefs, one of which is coral bleaching. We analyzed a global network of associations between coral species and Symbiodiniaceae for resistance to temperature stress and robustness to perturbations. Null networks were created by changing either the physiological parameters of the nodes or the structures of the networks. We developed a bleaching model in which each link, association, is given a weight based on temperature thresholds for specific host-symbiont pairs and links are removed as temperature increases. Resistance to temperature stress was determined from the response of the networks to the bleaching model. Ecological robustness, defined by how much perturbation is needed to decrease the number of nodes by 50%, was determined for multiple removal models that considered traits of the hosts, symbionts, and their associations. Network resistance to bleaching and robustness to perturbations differed from the null networks and varied across spatial scales, supporting that thermal tolerances, local association patterns, and environment play an important role in network persistence. Networks were more robust to attacks on associations than to attacks on species. Although the global network was fairly robust to random link removals, when links are removed according to the bleaching model, robustness decreases by about 20%. Specific environmental attacks, in the form of increasing temperatures, destabilize the global network of coral species and Symbiodiniaceae. On a global scale, the network was more robust to removals of links with susceptible Symbiodiniaceae than it was to removals of links with susceptible hosts. Thus, the symbionts convey more stability to the symbiosis than the hosts when the system is under an environmental attack. However, our results also provide evidence that the environment of the networks affects robustness to link perturbations. Our work shows that ecological resistance and robustness can be assessed through network analysis that considers specific biological traits and functional weaknesses. The global network of associations between corals and Symbiodiniaceae and its distribution of thermal tolerances are non-random, and the evolution of this architecture has led to higher sensitivity to environmental perturbations.

Coral reefs are degrading through the impacts of multiple anthropogenic stressors. How are coral reef communities going to change and how to protect them for future generations are important conservation questions. Using coral reef data from Mauritius, we examined changes in cover in 23 benthic groups for a 13-yr period and at 15 sites. Moreover, we determined which land-based stressor out of four (human population, agriculture, tourism, rainfall) correlated the most with the observed changes in coral reef cover. Among the stony corals, Acropora corals appeared to be the most impacted, decreasing in cover at many sites. However, the non-Acropora encrusting group increased in cover at several sites. The increase in abundance of dead corals and rubble at some sites also supported the observations of stony coral decline during the study period. Additionally, the decline in stony corals appeared to be more pronounced in second half of the study period for all sites suggesting that a global factor rather than a local factor was responsible for this decline. There was little change in cover for the other benthic groups, some of which were quite rare. Human population was significantly correlated with changes in coral reef cover for 11 sites, followed by tourism and agriculture. Rainfall, a proxy for runoff, did not appear to affect coral reef cover. Overall, our results showed that there has been a decline of stony coral cover especially the ones with complex morphologies, which in turn suggest that coral reefs around Mauritius have experienced a decline in habitat complexity during the study period. Our study also suggests that humans are an important factor contributing to the demise of coral reefs around the island.

Coral diseases are a leading factor contributing to the global decline of coral reefs, and yet mechanisms of disease transmission remain poorly understood. This study tested whether zooplankton can act as a vector for white band disease (WBD) in Acropora cervicornis. Natural zooplankton communities were collected from a coral reef in Bocas del Toro, Panama. Half of the zooplankton were treated with antibiotics for 24 h after which the antibiotic-treated and non-antibiotic-treated zooplankton were incubated with either seawater or tissue homogenates from corals exhibiting WBD-like symptoms. A total of 15 of the 30 asymptomatic A. cervicornis colonies exposed to zooplankton incubated in disease homogenate in tank-based experiments showed signs of WBD, regardless of prior antibiotic incubation. These results indicate that in our experimental conditions zooplankton were a vector for coral disease after exposure to disease-causing pathogens. Given the importance of heterotrophy on zooplankton to coral nutrition, this potential mode of disease transmission warrants further investigation.

Current trends demonstrate coral reef health in serious decline worldwide. Some of the most well-preserved coral reefs in the Caribbean basin are located in the waters surrounding Bonaire, in the Dutch Caribbean. In many places on the leeward side on islands dominated by trade winds, the shallow reef systems extend into deeper water where they are known as Mesophotic Coral Ecosystems (MCE). Autonomous Underwater Vehicles (AUVs) were used to collect geoacoustic data of these leeward reefs at multiple sites as part of an ocean exploration project. AUV swath bathymetry and side-scan sonar data were analyzed for depth, acoustic backscatter intensity, seafloor slope, and rugosity. These geomorphic metrics were then used as inputs to generate a composite synthetic index of bottom-type to delineate MCE features. A confusion matrix statistical analysis of the acoustic class map showed an overall accuracy of the acoustic classes at 66%, with accuracy of the hard coral class the highest at 83%, and the sandy-bottom class the lowest at 55. The hard coral class was also the statistically most reliable, at over 80%, with the noise class coming in as the least reliable. This morphologic habitat index is a potentially useful new tool in quantifying the extent of MCE located in proximity to Marine Protected Areas (MPAs).

Presented here is the initial hardware and software design of a prototype autonomous microplastic sampling instrument. Microplastics are defined as particles of plastic < 5 mm greatest dimension. They are becoming pervasive in the world ocean due to anthropogenic pollution. The ocean has spatially variable concentrations of surface microplastics, so attempting to identify trends in global dispersal patterns is difficult and expensive using current research techniques. Understanding the global dispersion patterns and degradation rates of microplastics will help to uncover the associated human and ecosystem impacts. A novel low-cost oceanographic sensor has been developed that can determine the concentration of marine microplastics over large spatial areas. This sensor can remove plastic particulates from seawater and archive them for later analysis, determine microplastic concentrations for 28 discrete samples recording GPS position, and simultaneously measure salinity and water temperature. This sensor has been designed around the open-source Arduino platform, allowing for maximum implementation of additional sensors and systems in future prototypes. The MantaRay sensor can be implemented on a drifter, mooring, or Autonomous Underwater Vehicle to gather diverse data on the dispersion of microplastics. This sensor could drastically cut research costs associated with studying deep-sea microplastic concentrations and increase our understanding of plastic dispersion and degradation rates in marine ecosystems.

Pressure increases rapidly with depth in a water body. Ocean and Great Lakes scientists often use this physical feature of water as the basis of a fun pastime performed aboard research vessels around the world: the shrinking of polystyrene cups. Depending on the depth to which the cups are deployed, the results can be quite striking! Capitalizing on this fascinating display of ocean physics, the authors describe an activity designed to familiarize students with the effects of increased water depth on pressure and volume. This activity incorporates ocean and aquatic sciences into classroom curricula, an important goal of the Ocean Literacy Campaign and associated Great Lakes Literacy Campaign. Students will develop hypotheses to investigate the effects of depth and thus pressure on the volume of polystyrene cups. To test their hypotheses, they will determine the volume of polystyrene cups before and after they are submerged to differing depths in the ocean and the Laurentian Great Lakes. Students will also calculate the density of the cups and learn about the depths of the world's ocean and the Great Lakes. This lab also encourages students to contact scientists and engage with professionals in the field of oceanography and limnology.

With support from the National Science Foundation, we report on a partnership between an academic institution (College of William & Mary's Virginia Institute of Marine Science) and an informal science education facility, the Watermen's Museum (Yorktown, Virginia) that puts professional-grade Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) into the hands of school groups. Our groups use these assets to conduct explorations of shipwreck sites from the last major battle of the American Revolution, the Battle of Yorktown. Students work in mission teams with objectives that change from session to session in ways reflective of actual expeditions using these technologies. Some examples of sessions include: deconstructing the system diagram of an ROV in order to troubleshoot its operation, measuring currents over the wreck site by timing particles passing by on the ROV's real-time video, recording biota seen on and around the wreck debris field, constructing a logical search pattern to locate a known wreck site, interpreting sidescan sonar imagery from sites thought to possess wrecks that may be eroding out of the sediment, and performing sophisticated maintenance, repair, systems checks, and upgrades to both robots. During vehicle deployments, students operate as a cross-trained team, with rotation of duties during deployment, including pre-launch system checker, deployer (into the water), navigator, data logger, chief mission supervisor, cable (ROV) or RF tracking (AUV) operator, and safety observer. We present the results of a formal evaluation by an outside evaluator, student attitudes toward science, and some of the student's “citizen science” conducted during this unique experiment in STEM education. Our results will be of use to other K-12 STEM efforts that use marine technology to engage student interest.

Water flow past corals may perform a number of functions during and following episodes of coral reef bleaching. Previous work has demonstrated that flow-modulated metabolism creates asymmetric bleaching patterns within a coral colony, but direct measurement of metabolic costs associated with bleaching have not been made at the level of the polyp. We examined the effects of flow on constitutive and regulated stress protein expression at the level of the polyp. We tested whether corals would exhibit a spatially asymmetric distribution of heat shock proteins 70 and 90 (hsp70 and hsp90) and the constitutive stress protein 70 (hsc70) related to velocity gradients (degree of mixing) across the coral colony. Flow manipulations were conducted from the NOAA underwater habitat Aquarius (FL, USA) on colonies of Montastrea annularis (Ellis and Solander, 1786), with controlled exposures to increased flow (ca. 40 cm s− 1) and increased temperature (ca. 1.5–2 °C above ambient) using in situ flow chambers. Single coral polyps were sampled, processed and analyzed for heat shock proteins using western blotting methods. The short term (daily) and medium term (9 days) response within discrete locations of the coral colonies were examined. We probed for three different stress proteins, with only one exhibiting asymmetrical patterns of synthesis across a colony. Montastrea annularis colonies developed and sustained significant spatially asymmetric patterns of stress protein synthesis across the entire coral surface, with upstream sectors expressing more hsp70, at the same time that these upstream sectors developed and sustained a reduced photosynthetic efficiency or Quantum Yield (QY). The mechanism producing this pattern is unclear; we speculate that increased flow may lead to an initial up-regulation within the synthesis of heat shock protein (hsp70) by the entire colony, followed by a down-regulation in discrete areas through increased hydraulic stress or biochemical energy requirements and limitations.

Recent studies have determined that water flow may perform a number of roles during and following episodes of coral reef bleaching. Increased water flow has the potential to improve the capacity of some scleractinian corals to cope with high concentrations of oxygen in the boundary layer that are photosynthetically derived, and coral reef damage is often at its highest in areas where flow is restricted. Conversely, water motion has been shown to increase metabolic rate (both photosynthesis and respiration) and such flow-modulated metabolism may affect bleaching patterns asymmetrically within a coral colony. To broaden these earlier studies and to further examine the effects of flow on photosynthetic efficiency, we tested to determine whether or not corals would exhibit a spatially asymmetric distribution of photosynthetic efficiency related to velocity gradients (degree of mixing) across the coral colony. We conducted experiments from the NOAA underwater habitat Aquarius on colonies of Montastrea annularis (Ellis and Solander, 1786) with controlled exposures to increased flow (ca. 40 cm s(-1), 1 cm above coral surface) and temperature (ca. 2 degrees C above ambient) using in situ flow chambers. We measured photosynthetic efficiency as a light-adapted quantum yield (F-v'/F-m') using Pulse Amplitude Modulation (PAM) fluorometry to examine the short-term (daily) and medium term (>= 9 days) response of patches of polyps within coral colonies. M annularis colonies developed and sustained a significant spatially asymmetric pattern of photosynthetic yield across the entire coral surface, with the upstream side of the colonies exhibiting reduced quantum yield. The mechanism producing this pattern is unclear; we speculate that increased flow may lead to increased photosynthesis by upstream polyps through bicarbonate delivery accentuated by the Q(10) effect. Local down-regulation of the photosynthetic response (decreased quantum yield) might then occur to keep tissue oxygen concentrations within tolerable limits. (C) 2007 Elsevier B.V. All rights reserved.

Callyspongia vaginalis, a common reef sponge in the Florida Keys, USA, exhibits depth-specific differences in bioenergetics and growth that are a function of food availability. We measured several physiological parameters in situ to construct the bioenergetic budgets of sponges living in deep and shallow waters. Respiration rates were measured in a recirculating flow respirometer and pumping rates were measured by filming dye ejected from sponge oscula. In addition, inhalent and exhalent water sampled from around sponge colonies at both depths was analyzed using flow cytometry to quantify the concentration and clearance rates of picoplankton. These parameters were used to construct an energetic budget for sponges from each depth and revealed that the scope for growth was substantially greater for deep sponges compared to shallow sponges, The greater scope for growth of deep sponges is likely due to the greater abundance of picoplankton in the deep versus shallow habitat. Both naturally occurring sponges and those used in a reciprocal transplant experiment between 12 and 25 m exhibited significantly greater growth in the deep than the shallow habitat. Hence, bottom-up forcing in the form of increased food availability may be of principal importance to the growth and physiological ecology of suspension-feeding sponges.

The recent development of the p)p-up satellite archival tag (PSAT) has allowed the collection of information on a tagged animal, such as geolocation, pressure (depth), and ambient water temperature. The success of early studies, where PSATs were used on pelagic fishes, has spurred increasing interest in the use of these tags on a large variety of species and age groups. However, some species and age groups may not be suitable candidates for carrying a PSAT because of the relatively large size of the tag and the consequent energy cost to the study animal. We examined potential energetic costs to carrying a tag for the cownose ray (Rhinopiera bonasus). Two forces act on an animal tagged with a PSAT: lift from the PSATs buoyancy and drag as the tag is moved through the water column. In a freshwater flume, a spring scale measured the total force exerted by a PSAT at flume velocities from 0.0) to 0.60 m/s. By measuring the angle of deflection of the PSAT at each vel( city, we separated total force into its constituent forces-lift and drag. The power required to carry a PSAT horizontally through the water was then calculated from the drag force ani velocity. Using published metabolic rates, we calculated the power for a ray of a given size to swim at a specified velocity (i.e., its swimming power). For each velocity, the power required to carry a PSAT was compared to the swimming power expressed as a percentage, %TAX (Tag Altered eXertion). A %TAX greater than 5% was felt to be energetically significant. Our analysis indicated that a ray larger than 14.8 kg can carry a PSAT without exceeding this criterior. This method of estimating swimming power can be applied to other species and would allow a researcher to decide the suitability of a given study animal for tagging with a PSAT.

Although squid are among the most versatile swimmers and rely on a unique locomotor system, little is known about the swimming mechanics and behavior of most squid, especially those that swim at low speeds in inshore waters. Shallow-water brief squid Lolliguncula brevis, ranging in size from 1.8 to 8.9 cm. in dorsal mantle length (DML), were placed in flumes and videotaped, and the data were analyzed using motion-analysis equipment. Flow visualization and force measurement experiments were also performed in water tunnels. Mean critical swimming speeds (U-crit) ranged from 15.3 to 22.8 cm s(-1), and mean transition speeds (U-t; the speed above which squid swim exclusively in a tail-first orientation) varied from 9.0 to 15.3 cm s(-1). At low speeds, negatively buoyant brief squid generated lift and/or improved stability by positioning the mantle and arms at high angles of attack, directing high-speed jets downwards (angles > 50 degrees) and using fin activity. To reduce drag at high speeds, the squid decreased angles of attack and swam tail-first. Fin motion, which could not be characterized exclusively as drag- or lift-based propulsion, was used over 50-95 % of the sustained speed range and provided as much as 83.8 % of the vertical and 55.1 % of the horizontal thrust. Small squid (<3.0 cm DML) used different swimming strategies from those of larger squid, possibly to maximize thrust benefits from vortex ring formation. Furthermore, brief squid employed various unsteady behaviors, such as manipulating funnel diameter during jetting, altering arm position and swimming in different orientations, to boost swimming performance. These results demonstrate that locomotion in slow-swimming squid is complex, involving intricate spatial and temporal interactions between the mantle, fins, arms and funnel.