Comparison of methods used to estimate coral cover in the Hawaiian Islands

Abstract

Nine coral survey methods were compared at ten sites in various reef habitats with different levels of coral cover in Kāne‘ohe Bay, O’ahu, Hawaiʻi. Mean estimated coverage at the different sites ranged from less than 10% cover to greater than 90% cover. The methods evaluated include line transects, various visual and photographic belt transects, video transects and visual estimates. At each site 25 m transect lines were laid out and secured. Observers skilled in each method measured coral cover at each site. The time required to run each transect, time required to process data and time to record the results were documented. Cost of hardware and software for each method was also tabulated. Results of this investigation indicate that all of the methods used provide a good first estimate of coral cover on a reef. However, there were differences between the methods in detecting the number of coral species. For example, the classic “quadrat” method allows close examination of small and cryptic coral species that are not detected by other methods such as the “towboard” surveys. The time, effort and cost involved with each method varied widely, and the suitability of each method for answering particular research questions in various environments was evaluated. Results of this study support the finding of three other comparison method studies conducted at various geographic locations throughout the world. Thus, coral cover measured by different methods can be legitimately combined or compared in many situations. The success of a recent modeling effort based on coral cover data consisting of observations taken in Hawai‘i using the different methods supports this conclusion.

Daily variation in net primary production and net calcification in coral reef communities exposed to elevated <i>p</i>CO<sub>2</sub>

“…This community consisted of Porites compressa (7 % cover), Montipora capitata (12 %), massive Porites spp. (3 %), and Pocillopora damicornis (2 %), and the crustose coralline alga Porolithon onkodes (4 %) (Jokiel et al, 2015). As described above for Experiment 1, sediments were inserted into the floor of the flume to recreate ecologically relevant communities.…”

Coral bleaching susceptibility is predictive of subsequent mortality within but not between coral species

“…This discrepancy could be due in part to the low mortality of bleaching resistant phenotypes masking the higher mortality of bleaching-susceptible individuals in community wide surveys. In addition, the high variance of photoquadrat surveys makes it difficult to detect small changes in benthic cover (Jokiel et al , 2015). Photoquadrat surveys are also commonly used to quantify recently dead coral cover during or following a bleaching event, however this method cannot discern whether the coral that died had in fact bleached, whereas individual colony data revealed the consequences of thermal stress for both bleaching phenotypes.…”

Responses of Herbivorous Fishes on Coral Reef Cover in Outer Island Indonesia (Study Case: Natuna Island)

“…A principal focus of percent cover from 3 standard benthic categories HC, DC and DCA of its functional roles as a key builder of reef structure and a key provider of complex, rigid habitat for much another reef biodiversity especially for herbivore fish diversity [25,34]. Cover by substrate type was evaluated from 11 sites underwater photographic transects (UPT) [35,36,37] of 50 m length. The digital photograph was taken parallel on quadrat transect modification by [38] with dimension 58 x 44 cm at a height of 1.20 m, with approximately 1 m of distance between each photo.…”