Application Story

  1. Could you describe the research work you and your colleagues at the Bermuda Institute of Ocean Sciences BIOS are doing with respect to coral reef health?

    The Coral Reef Ecology and Optics Laboratory (CREOL) conducts both applied and basic research to understand how coral reef ecosystems function and respond to natural and anthropogenic forcings. To address different aspects of the reef ecosystem, a combination of both traditional and more novel high-technology methods are used in the lab, including:

    • Diver-based surveys to assess benthic and fish communities;
    • Measuring seawater chemistry to describe the environment in which reef organisms live;
    • Remote sensing to assess a reef's biological communities; and
    • Optics to study how the benthic community utilizes light in an effort to understand ecosystem function.

    The applied research component of CREOL is the Marine Environmental Program (MEP). MEP is funded annually by the Government of Bermuda Department of Environmental Protection to help meet the Department's mission to protect Bermuda's environment by conducting routine monitoring of marine resources. The baseline objectives for MEP are to:

    • Provide long-term data sets to assess the health and status of the marine environment;
    • Detect changes in the marine environment;
    • Understand the significance of existing sources of pollution;
    • Identify new potential sources of pollution; and
    • Delineate the effects of local and regional (climate-related) stresses.
  2. What role does water temperature monitoring play?

    Water temperature is one of the key environmental variables in the coral reef environment. At the fine scale, water temperature directly affects biological and chemical reactions. At the broader scale, water temperature has long been considered one of the main factors controlling coral reef distribution. Bermuda is the northernmost coral reef system in the Atlantic Ocean.

  3. Where have you deployed temperature loggers?

    The Seawater Temperature Monitoring Program (STMP) consists of 11 locations across the Bermuda platform, encompassing different physiographic reef zones. Monitoring locations were chosen to complement ecological assessments of the status and trends of the reef benthic community. This includes areas such as Castle Harbour, John Smith’s Bay Beach, and Long Bay Beach.

  4. Can you describe your logger deployment methods?

    Generally, I use pairs of HOBO U22 Water Temp Pro loggers for in situ data collection at reef sites. Prior to deployment, all loggers are calibrated and tested for their operational status, e.g. battery life and connectivity. Pairs of loggers are deployed per site (redundancy) with the sampling regime set at 30-minute intervals. Ultimately we are interested in maximum, minimum, and daily average temperatures. Once logging, loggers are housed in the protective boots and caps provided by Onset. As deployments are for approximately 12-month periods, loggers are wrapped in electrical tape for additional protection against fouling, but making sure the sensor remains uncovered. Over the years I have found it saves time and increases the working life of the loggers. I find it helpful to use a small strip of matching colored tape per pair of loggers. This makes for easy identification during deployments.

    All loggers are attached to rebar stakes that have been hammered and cemented into the reef using stainless steel hose clamps and cable ties.

  5. Why did you choose the larger HOBO U22 water temperature loggers over the more compact TidbiT or HOBO Pendant loggers?

    We like the size of the U22 loggers because they are big enough to see physical evidence of the loggers still being attached to the stakes without having to be right next to them. We also find them easy to handle during deployment.

  6. What are some of the challenges you face with respect to deploying loggers and/or retrieving data?

    It’s not necessarily a major challenge, but Damselfish can be a problem. We find they have a tendency to make the stake/logger combination the center of their territory. Being highly territorial means having to deal with very agitated fish come retrieval time!

  7. What are typical sample rates for the kind of data you’re collecting?

    For 12-month field deployments we use 30-minute intervals. However, in experimental situations it can be as fine scale as 5-second intervals.

  8. How often is data offloaded and analyzed?

    This depends on the project, but STMP is annual; experiments can range from hourly to daily. Later this year, I plan to use data loggers attached to a mooring line at set depths to give temperature profiles. These will be analyzed daily.

  9. What are some of the key findings from the water temperature data you’ve collected?

    Coral bleaching events have been documented in Bermuda. In light of predicted increases in seawater temperature through climate change, the potential for recurrent coral bleaching events, and increased prevalence in disease, the network of loggers affords us a greater understanding of the spatial-temporal seawater temperature trends around Bermuda’s platform.

    Apart from developing a long-term time series of temperature records for the reef environment, the loggers have allowed us to identify meteorological events. The loggers were able to detect rapid significant drops in water temperature (2º to 4°C) associated with the cooling of sea surface temperatures caused by passing hurricanes and tropical storms. Secondly, the loggers have recorded pronounced cooling (5º to 7°C), which is believed to be due to upwelling deeper seawater, possibly through internal waves. The possibility of such events is still being investigated.