15 m DEPTH CORAL REEF MONITORING SURVEY SITE: OVERVIEW OF
METHODOLOGIES
Section 1: Survey site overview and goals
15 m survey site: instruments, surveys, collections—The coral reef monitoring survey site is
a 5 m x 10 m rectangle (Figure 1), oriented parallel to the shoreline/reef slope, with the
down reef slope azimuth represented by the 5 m sides and the cross reef slope azimuth
represented by the 10 m sides. Deployed on the reef for a period of 3 years within the 5 m x
10 m survey site are a suite of instruments which aid in the monitoring of reef biodiversity,
reef calcification rate, reef bioerosion rate, and seawater temperature variability: 3
Autonomous Reef Monitoring Structures (ARMS), 5 Calcification Accretion Units (CAUs), 5
Bioerosion Monitoring Units (BMUs), and 1 Seabird Electronics, SBE-56
(http://www.seabird.com/sbe56-temperature-logger) temperature logger.
Deployment of the 15 m survey site— The exact location of the 15 m survey site is
recorded through a global positioning system (GPS) waypoint and hand written log sheets
documenting activities and notes about the survey site. The survey site’s rectangular shape
is measured with measuring tape and delineated on the reef by temporarily placing tapes
and markers during installation. Along one 5 m side and one 10 m side of the survey site,
the measuring tape is used to mark a 15 m transect of reef for photographic
documentation, urchin counts, and reef structure rugosity measurements. SCUBA divers
photograph the reef at 1 m intervals on both sides of the tape (30 total photographs over
the 15 m transect), as well as conduct an urchin count and evaluation of reef rugosity within
the same thirty 1 m segments. Around the perimeter of the survey site, at 5 m intervals,
the CAUs and BMUs are deployed on the reef. Within the 50 m2 area of the survey box the
ARMS and SBE-56 are placed. While SCUBA divers are at the survey site a discrete near reef
(15 m depth) seawater sample is collected using a 5 L Niskin bottle and during the ascent to
the surface another discrete water sample is taken within the water column at 1 m depth
directly above the 15 m survey site. Immediately upon returning to the dive boat, a
conductivity-temperature-depth (CTD) hydrocast of the water column above the 15 m
survey site is collected using a SBE-19plus (http://www.seabird.com/sbe19plusv2-seacatctd). Next, the surface (1 m) and reef (15 m) seawater samples are processed for DIC, TA,
nutrients, and/or salinity analyses.
Monitoring goals for the 15 m survey site— The 15 m survey site design follows the climate
monitoring themes set forth in NOAA’s National Coral Reef Monitoring Plan (NCRMP). The
primary focus of the climate change portion of NCRMP is to monitor spatial and temporal
variability in thermal stress and ocean acidification. A secondary focus is to identify the
ecological impacts related to warming ocean temperatures and a dropping pH.
Deployments of SBE-56 temperature loggers (5 min sample rate for 3 year deployments)
provides high resolution, accurate, temperature time series. The analysis of each seawater
sample for DIC and TA, in concert with the salinity, temperature, and depth data provided
by the SBE-19plus, facilitates calculating inorganic carbon system parameters (pH,
saturation states: Ωarag and Ωcalc, [CO2*], [HCO3-], [CO32-], etc.) at each 15 m survey site.
Deployments of CAUs, ARMS, and BMUs address the secondary interests in ecological
impacts of climate change: net calcification rates, coral growth rates, bioerosion rates, and
cryptic biodiversity and community structure variability.
Figure 1: 15 m survey site diagram outlining the 5 m x 10 m shape, as well as, the deployment of 3 ARMS, 5 CAUs, 5 BMUs,
1 SBE-56 (subsurface temperature recorder STR), the collection of a near reef seawater sample, and the 15 m linear
transect used for photographic documentation and ancillary reef measurements.
Section 2: Additional research projects occurring at the 15 m survey site
Coral coring of Porites spp. massive corals—At least 3 coral colonies, within or very near the
15 m survey site, are selected for sampling. CRED scientists drill the corals while on SCUBA
using either a pneumatic hand-held drill or a larger surface powered hydraulic drill. The
pneumatic drill can be easily operated by a diver team of 2, whereas the hydraulic drill
requires a larger dive team and surface support on small boats. The pneumatic drilling
technique is preferred when a core length of greater than 100 cm is NOT required. Using a
pneumatic drill and specialized coring bit, a core sample of 3.5 cm in diameter x 10-90 cm in
length can be recovered. The hydraulic drill recovers cores of 12.5 cm in diameter x 30-700
cm in length. For further information regarding coral drilling, please contact CRED scientists
Rusty Brainard (rusty.brainard@noaa.gov) or Tom Oliver (thomas.oliver@noaa.gov).
Diurnal sampling of the chemical and physical reef environment—CRED has assembled a
suite of instrumentation to quantify the diel variability in carbonate chemistry at the reef.
The development of this instrument suite was motivated by a desire to measure the highly
variable carbonate system parameters within a reef ecosystem around the clock. Field
monitoring efforts onboard a research ship are limited to daylight hours, thus night-time
processes occurring on the reef were not sampled. The result was the development of
CRED’s Ocean Acidification Diurnal Suite (Figure 2), which is deployed by SCUBA divers onto
the reef, within the 15 m survey site area, and left to autonomously sample for 24 hours. The
diurnal suite consists of: 1 SBE-19plus CTD (moored mode, 5 min interval), 1 Nortek 2.0 MHz
Acoustic Doppler Current Profiler (ADCP) (moored mode, 5 min interval, sampling current
direction and magnitude over 15, 1m depth bins: http://www.nortekas.com/en/products/current-profilers/aquadopp-profiler), 1 Satlantic SeaFET Ocean pH
sensor (moored mode, 30 min interval, measuring in-situ pH: http://satlantic.com/seafet),
and 7 Programmable Underwater Collectors (PUC), designed by Dr. Chris Langdon at
University of Miami (clangdon@rsmas.miami.edu), where each instrument collects 1
discrete water sample at a pre-programmed date/time (CRED uses 4 hr intervals with 7 PUCs,
e.g. 1200 (day 1), 1600, 2000, 0000, 0400, 0600, 1200 (day 2)). The Diurnal Suite of
instruments supports the already occurring discrete water sampling by extending CRED’s
monitoring effort through recording an ever changing diurnal DIC/TA signal, identifying the
residence time of the seawater “carrying” the chemical signal, and a high resolution in-situ
pH time series at the reef.
Figure 2: Ocean Acidification Diurnal Suite deployed on the reef at Jarvis Island. In the foreground is a newly deployed ARMS,
with a SBE-19plus and SeaFET behind it. The PUCs are deployed vertically in the yellow crates and center photo is the ADCP.