Mark R. Patterson

Effects of morphology and water motion on carbon delivery and productivity in the reef coral, Pocillopora damicornis (Linnaeus): Diffusion barriers, inorganic carbon limitation, and biochemical plasticity

Abstract Colonies of the reef coral Pocillopora damicornis (Linnaeus) taken from high and low flow habitats at the same depth and light regime show significant differences in colony morphology but not Reynolds numbers. Because Reynolds numbers are similar, dynamic similarity predicts that the flow patterns, and thickness of the diffusional boundary layer are quantitatively identical. Measurements of chlorophyll content per cell, antioxidant enzymes, and carbonic anhydrase all indicate similar levels of productivity between corals from high and low flow environments. When specimens of P. damicornis exhibiting the high flow morphology were placed in microcosms and allowed to acclimatize for 13 days to different flow regimes they exhibited a significant increase in the activities of all antioxidant enzymes, photosynthesis, and respiration with increasing water velocity. A non-dimensional analysis using Sherwood/Reynolds number plots also showed a significant augmentation of net photosynthesis with increasing water flow. Carbonic anhydrase in the host tissues showed an inverse relationship with water velocity, while the productivity and specific activities of ribulose bisphosphate carboxylase oxygenase of the zooxanthellae show a direct relationship with water velocity. These results suggest that: (1) morphological plasticity of the coral skeleton under different flow regimes provides a mechanism that minimizes diffusional boundary layer thickness and maximizes carbon delivery to the site of fixation under different flow regimes, and (2) when a coral with a fixed skeletal morphology is exposed to a new flow regime, physiological and biochemical plasticity can augment the delivery of carbon to the site of assimilation.

Collaborative Autonomous Surveys in Marine Environments Affected by Oil Spills

This chapter presents results on collaborative autonomous surveys using a fleet of heterogeneous autonomous robotic vehicles in marine environments affected by oil spills. The methods used for the surveys are based on a class of path following controllers with mathematically proven convergence and robustness. Use of such controllers enables easy mission planning for autonomous marine surveys where the paths consist of lines and curves. The control algorithm uses simple dynamic models and simple control laws and thus enables quick deployment of a fleet of autonomous vehicles to collaboratively survey large areas. This enables using a mobile network to survey an area where the different member nodes may have slightly different capabilities. A mapping algorithm used to reconcile data from heterogeneous marine vehicles on multiple different paths is also presented. Vehicles with heterogeneous dynamics are thus used to aid in the reconstruction of a time varying field. The algorithms used were tested, mainly on student-built marine robots that collaboratively surveyed a coastal lagoon in Grand Isle, Louisiana that was polluted by crude oil during the Deepwater Horizon oil spill. The results obtained from these experiments show the effectiveness of the proposed methods for oil spill surveys and also provide guidance for mission designs for future collaborative autonomous environmental surveys.

Controller performance of marine robots in reminiscent oil surveys

A class of path following and formation controllers are implemented on marine robots performing autonomous surveys in regions polluted by crude oil during the Deepwater Horizon oil spill. The controllers enable the robots to follow lines and curves, and maintain formation collectively while measuring reminiscent crude oil along their paths. The controllers are mathematically sound with proven convergence and robustness. However, their performance in the surveying missions is affected by natural disturbances caused by wind and water currents, and constraints such as sensor inaccuracy, localization errors, and network delays. This paper evaluates the performance of our controllers based on data collected during a survey performed at Grand Isle, Louisiana. These results will provide guidance for mission designs and inspire the future developments of our marine robots used to perform autonomous environmental surveys.

Mesophotic Coral Ecosystems: A Geoacoustically Derived Proxy for Habitat and Relative Diversity for the Leeward Shelf of Bonaire, Dutch Caribbean

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).

Zooplankton as a potential vector for white band disease transmission in the endangered coral, Acropora cervicornis

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.

MantaRay: A novel autonomous sampling instrument for in situ measurements of environmental microplastic particle concentrations

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.

Observing and modeling global warming impacts in Virginia

Until recently, oceanographers had a big problem: the ocean changes faster than our ability to observe it. In the coastal zone and estuaries like Chesapeake Bay, the changes can be even faster. Recently, marine scientists, with the backing of the US Congress, have been building ocean observing systems. These are networks of sensors, above and below the water, some of them mobile, most of them fixed. These networks deliver data to computers that run mathematical models and make predictions useful to the public or government.