Reef Havens Research Project (Temperature, Current, CTD casts at Moore Reef) 2018 - 2021

The dataset consists of multiple data files from four types of instruments to visualize current, temperature flow patterns and coral stress responses around the north west section of Moore Reef including a reef pass, taken during 2018-2021. These include 19 temperature and 12 current loggers and 69 CTD casts, along with fluorometry measurements of 33 tagged coral colonies. This dataset also includes photos of the tagged corals along with CoralWatch colour cards during a 5-week period from Nov-Dec 2020.

The three-year Reef Havens Research Project commenced in December 2017 in response to the unprecedented back-to-back coral bleaching events on the Great Barrier Reef in 2016 and 2017. The proposal was based on anecdotal observations during those bleaching events that local environmental conditions were a significant factor affecting bleaching severity and recovery after bleaching: reefs that were near upwellings, or experienced cooler currents or wind mixing, tended to experience less severe bleaching, and those with few other pressures tended to recover better. Could science-based localised interventions that mimic these natural stress-reducing phenomena (for example by incrementally increasing water movement, reducing water temperature by 1-2°C, or disrupting the water’s surface) reduce coral stress, bleaching severity and/or promote recovery on key reef sites, potentially providing time and space for natural acclimatization and adaptation processes to occur?

The Reef Havens Research Project is a foundational investment in an in?situ research platform that was intended to closely observe the impacts of changes in flow and temperature on coral stress, bleaching and recovery outcomes at the very small scale of a tourism site. Once small-scale water movements associated with bleaching events were understood, the project also tested whether an engineering intervention could restore “normal” water movement and mixing during doldrum coral bleaching conditions at a very small area of Moore Reef, one of the key tourism industry sites on the GBR near Cairns. It is hoped that the data generated through this research project will be used by others to build further understanding of the connection between environmental conditions and coral stress, and the potential for interventions to improve bleaching outcomes at small scales.

Methods:

To quantify current and temperature flow patterns and their impacts through the Moore Reef Pass and adjacent tourism site areas, an array of instruments was deployed. The instruments used were a Marotte HS current meter, HOBO TidbiT MX Temp 400 logger, a Walz DIVING-PAM-II underwater fluorometer and a SonTek Castaway conductivity, temperature and depth recorder (CTD).

The Marotte HS current meter is a drag-tilt current meter, developed and manufactured by the Marine Geophysics laboratory at James Cook University. The instrument consists of a buoyant enclosure containing an electronic logger, which is then fixed to a stationary point. The buoyancy force causes the instrument to float directly upwards in the absence of current. Movement of the water exerts a drag force on the instrument, tilting it over until the buoyancy, drag and tether forces are balanced. The amount of tilt is proportional to the speed of the water. The logger records the tilt angle using an accelerometer, and the tilt direction using a magnetometer. Both tilt and tilt angle were converted to current speed and direction in post-processing using a pre-defined tilt-to-speed calibration curve. The instrument also contained a temperature sensor (thermistor type with ±0.2C repeatability) that was fixed to the bottom of the logger (JCU and Marine-Geophysics-Laboratory, 2017).

An array of 12 current meters were fixed to star pickets 0.5 m above the substrate (see Marotte deployment picture) at selected locations, substrate types and depths through the reef pass and tourism pontoon areas for 5 deployments between 2018 and 2021 (see downloadable documents for details of deployments). The loggers were set to record current speed and direction (in m/s and degrees) at one second intervals, along with temperature in Celsius at one-minute intervals. The data were recorded on a micro SD card and the instrument was powered by 2 AA batteries. The raw data were converted into current speed and direction and temperature to one minute intervals with the Marotte HS config program (JCU and Marine-Geophysics-Laboratory, 2017). Along with each csv file per instrument per deployment there is a metadata text file containing the calibration and processing information. All 12 current meters were removed and data downloaded on the 13-Sept-2018.

Nineteen HOBO TidbiT MX Temp 400 loggers were installed at various depths at the northern section of Moore Reef (see Moore Reef Hobo Map) for 4 deployments between 2018 and 2021 (see downloadable document for details of deployments). Some loggers were fixed to star pickets at ~ 50cm above the substrate and others were fixed to mooring lines. The loggers recorded temperature in Celsius at five-minute intervals and at this ratio had nominal battery life of 340 days. The data were downloaded using HOBO’s mobile phone app and are provided as CSV files.

To investigate changes in coral stress associated with water movement, 33 corals from 11 species located along pre-existing monitoring sites were selected and tagged with labelled cattle tags (see downloadable document for details). These individual colonies were underwater photographed with a CoralWatch card in which a finger was visible pointing to the colour on the card that matched the colour of the colony. Sampling was conducted once a week over 5 weeks Nov-19 to Dec-20. The intent was to compare coral stress levels in early summer, during well-mixed conditions, with late-summer, stratified, potentially bleaching conditions. Baseline early-summer stress measurements of these colonies were made with the Walz DIVING-PAM-II underwater fluorometer in 2019 but unfortunately we were prevented from accessing the tagged corals during late summer (March 2020), even though some bleaching was reported, when coronavirus restrictions shut down the GBR tourism industry. Instead we repeated the late-summer fluorometer measurements in April 2021, even though conditions were not stratified. Data were downloaded using Walz’s fluorometry software.

The CastAway CTD enabled near-instantaneous vertical profiles of temperature and salinity to be obtained at and around our field site at Moore Reef.

The CastAway CTD was deployed using a modified fishing rod and 200 lb breaking strain braid Dyneema fishing line either directly from the back of the Reef Magic Marine World Pontoon or via a small tender. The instrument was allowed to sink to the bottom and then rapidly retrieved, making measurements both on the way down and on the way up. The CastAway recorded the GPS location before and after each cast. Plots of conductivity, temperature, salinity and sound speed versus depth could be viewed immediately on the CastAway's integrated color LCD screen in the field. A total of 69 casts were performed, with each cast collecting ~100 data points. Raw data were downloaded via Bluetooth to a Windows computer for detailed analysis and/or export.

Limitations of the data:

The first and last 24 hours of the Marotte and HOBO logger datasets should be treated with caution as this may include transportation time to and from deployment site. Current Meter 12 stopped recording on the 21-Jun-2018.

The CastAway CTD was deployed on an event-based basis, enabling comparison of patterns during normal well-mixed conditions and also during calm, sunny doldrum conditions when normal mixing had failed. Two different instruments were used during the 2019-2020 sampling period, with differing calibration history. While the conductivity measurements should therefore be treated with caution, the temperature data are considered reliable.

Format:

The data set contains multiple parts which are the Marotte current meters, Hobo Temperature meters, CTD casts and fluorometry/coral watch data.

The Marotte current meter dataset consists of individual csv files for 12 instruments for 5 deployments (see downloadable documents for details of deployments).

The HOBO temperature meters datasets consist of individual csv files for an array of HOBO loggers for 4 deployments (see downloadable documents for deployment details).

The CTD datasets consist of CSV files for deployments on each of three dates. Please note that these deployments were deliberately performed on particular dates to measure extreme conditions of stratification, and their deviation from normality, rather than an attempt to rigorously document conditions over time.

The coral watch data consist of two photos for each colony, the first with a close up of the labelled cattle tag and the second showing the coral watch card colour reference matched to coral colony colour. There are 5 folders labelled according to sampling date. This also includes a CSV file with the PAM data.

Data Dictionary:

- This dataset consists of data files compiled from 12 Marotte HS current meters over 5 deployments at Moore Reef Pass (see Moore Reef Marotte Map) between May-18 and Aug-20. The spreadsheet for each Marotte contains the processed data of: Timestamp (one minute intervals), Current Speed (m/s), Direction (degrees), Speed Upper (m/s), Speed lower (m/s), Tilt (radians), Direction (radians), Battery (Volts) and Temperature (Celsius).

- This dataset also consist of HOBO temperature logger data, that recorded water temperature (Celsius) and Timestamp (5 minute intervals) for 4 deployments between Jun-20 and Aug-20.

- The dataset contains 5 folders under coral watch colonies, with each folder containing jpeg photos of tagged coral colonies.

- PAM data:
Type = F (fluorometer) or SPEC (Spectrophotometer)
No. = measurement number by this fluorometer (for its own internal record-keeping)
1:Mark = coral colony tag as referred to in the “Pam transect species list” that I’ve just uploaded
1:F = Light adapted minimum fluorescence
1:Fm1 = maximum fluorescence
1:PAR = photosynthetically active radiation
1:Y (II) = effective quantum yield of Photosystem II
1:ETR = electron transport rate

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\custodian\2020-2029-other\Reef-Havens