Dr. Scott Gallager (WHOI) in collaboration with Dr. Satoshi Mitari (OIST), PI.
The OIST OceanCubes observatory establishes a local control volume for high resolution measurements of water column processes coupled with observations of coral reef and fish community health. The OIST OceanCube is ~90 x 90m at a depth of 20m encircled by four thermister chains extending from the seafloor to the surface with four uplooking ADCPs to measure flux of water, energy and materials through the volume. A central electronics node is cabled to shore via electro-optical cable to provide power and real-time communications. Sensors on the node include temperature, salinity, pressure, chlorophyll, particle backscatter, CDOM, downwelling irradiance (PAR) at two depths, and plankton abundance ( Continuous Particle Imaging and Classification System-CPICS). Two stereo cameras with image processing and machine vision tools capture color- and size-corrected observations of fish communities as well as their responses to physical and geochemical gradients. Upgrades of the observatory will include database and web-services for rapid data extraction for synthesizing the data streams and to provide data products useful for addressing a multitude of scientific questions by OIST and WHOI scientists and the community as a whole.
The CPICS imaging system takes pictures of plankton 20 to 900um in size allowing meroplanktonic larvae and holoplankton to be quantified over time. A machine vision plankton classifier will provide rapid identifications to taxonomic group providing a temporal history of plankton biodiversity as a function of physical and chemical forcing. Installation of a second OceanCube on the Island of Oshima 1000 km to the north will allow transport of materials, larvae and evolution of the plankton community during the 5 to 6 days travel time between observatories, both located in the heart of the Kuroshio Current.
The seawater carbonate (CO2) system is traditionally characterized by four primary parameters – partial pressure of CO2 (pCO2) or CO2 fugacity (fCO2), total dissolved inorganic carbon (DIC), pH, and total alkalinity (TA). Ocean acidification is changing the seawater carbonate system in an unprecedented way as more anthropogenic CO2 dissolves into seawater due to atmospheric CO2increase.This pH lowering process is decreasing carbonate saturation states and affecting many chemical, biological, ecological and even physical processes in the ocean. Development of in-situ sensor technologies for CO2 parameters has been widely recognized as a research priority in the carbon and ocean acidification research community. This stems from the need to study dynamics of the marine CO2 system on various temporal and spatial scales. In many cases, traditional bottle sampling and analysis cannot achieve sufficient data coverage. The OIST OceanCube represents a unique oasis for coral reef ecosystems and associated biological processes that are highly vulnerable to OA. The reason for this vulnerability is the seasonal upwelling of water that is cold, nutrient rich, oxygen poor, low in pH, and corrosive (undersaturated with respect to aragonite). Similar to other coastal OA ‘hot spots’, such as the U.S. west coast and the Pacific coast of Panama, the upwelling predisposes the region to be relatively more sensitive to OA effects as a result of already low pH and carbonate saturation states.
The plankton community appears to be dominated by a Acantherian (Acantherioma sp.), which build celestite skeletons from strontium sulfate (see images this page). This material is very sensitive to low pH making this organism a useful sentinel organism for monitoring the impact of OA on the plankton community.
Reef fish assemblages are being quantified over a variety of temporal scales: hourly, daily, monthly, interannually, seasonally, diurnally (e.g. activity vs. time of day), and in relation to storms (cyclones), and fine-scale physical processes such as internal-waves. Internal waves impose dramatic changes in temperature, nutrients, and dissolved oxygen. For example, at our Panama site, internal waves with a period of 10 minutes expose fish and benthos to a 10ºC change in a matter of seconds (Gallager et al., 2008). Such a drastic change may be a driver for a variety of fish behaviors. We hypothesize that the OIST site will have more variable fish assemblages during times of the year when internal waves are present (dry season). There may also be a shift in the percentages of each trophic group compared to the rest of the year in response to the drastic changes being imposed by the internal waves. We further hypothesize that this shift in dominance of trophic groups will not be seen in the wet season when there is not as much environmental instability.
The region around Motobu Point where the Ocean Cube is located suffered a major coral bleaching event in the early 1990’s. By locating the cameras at this location, long term monitoring of growth and resilience to this bleaching event will be characterized. To date we have identified over 40 species of coral at this site. Given the relatively harsh conditions provided by rapid changes in temperature, we can hypothesize that the more robust species such as Acropora and Porities will rebound more rapidly than others. This project is highly novel in the proposed temporal scale of hydrographic, plankton, and fish detection. Sampling these factors at 1Hz on a period of years will provide both long temporal scale measurements such as inter-annual comparisons as well as fine-scale correlations with physical processes such as internal waves. The technical aspects of sampling at such a high rate is not insignificant and requires enhanced data serving capabilities, webservices, and automated detection and classification methods, which will be addressed in future upgrade projects.
1. A single cell amoeboid protozoa (Acantherian: Acantherioma sp.), which builds its skeleton from celestite (strontium sulfate) and is very sensitive to acidification. Size: ~ 55 um 2. A radiolarian. Diameter ~50 um is very abundant upwards of 100 individuals/L. 3. A diatom Rhizosolenia sp. (Bacillariophyceae). Diameter: ~20 um.
A spectrogram from a hydrophone attached to the pan and tilt camera. This spectrum has a large feature corresponding to boat noise. Fish vocalizations can also be heard. Listen HERE.
Divers during assembly of the main node.
A school of dory snapper (Lutjanus fulviflamma).