[Coral-List] Surveying coral reef biomass in 3D

Niklas Kornder niklaskornder at googlemail.com
Thu Jul 1 06:21:01 UTC 2021


Dear listers,

I would like to inform you on our most recent publication in Coral Reefs 
entitled ‘Implications of 2D versus 3D surveys to measure the abundance 
and composition of benthic coral reef communities’ (see below for full 
publication details).

A paramount challenge in coral reef ecology is to estimate the abundance 
and composition of the communities residing in such complex ecosystems. 
Traditional 2D projected surface cover estimates neglect the 3D 
structure of reefs and reef organisms, overlook communitiesresiding in 
cryptic reef habitats (e.g. overhangs, cavities), and thus may fail to 
represent biomass estimates needed to assess trophic ecology and reef 
function. We show that different abundance metrics (2D cover, 3D surface 
area, biovolume, biomass) lead to markedly different perspectives on 
benthic reef community composition on 12 coral reef slopes on the island 
of Curaçao (Southern Caribbean). Approximately half of the surveyed 
reef’s surface and biomass is ‘hidden’ in cryptic habitats. Where 2D 
cover was dominated (52 % of total benthos) by non-calcifying 
phototrophs (macroalgae, turf algae, benthic cyanobacterial mats), their 
contribution to total reef biomass was minor (3.2 %). In contrast, where 
sponges represented only 1.6 % of the benthos on 2D-projected reefs, 
they were estimated to be the largest benthic group (53 %) in terms of 
biomass, most of which cryptic and thus undetected in traditional surveys.

Our new report includes:

  * a guide to surveying reefs in 3D using open-source software + action
    cameras (GoPros)
  * biomass conversions for all major benthic coral reef taxa from
    surface area and biovolume to ash-free dry weight, organic carbon,
    and organic nitrogen

Without disregarding traditional coral point counts and Co., we propose 
new types of baselines for more comprehensive reef community assessments 
serving various ecological questions. As traditional surface cover data 
overlooked ~50 % of the reef’s biomass (mainly cryptic fauna that 
differs from exposed benthic communities), such 3D baselines can aid in 
the evaluation of the contributions of different taxa in biogeochemical 
processes and community dynamics.

I look forward to presenting an overview of this work at the upcoming 
ICRS in session 11c and we are happy to discuss the outcomes of our paper.

Kornder NA, Cappelletto J, Mueller B, Zalm MJ, Martinez SJ, Vermeij MJ, 
Huisman J, de Goeij JM (2021) Implications of 2D versus 3D surveys to 
measure the abundance and composition of benthic coral reef communities. 
Coral Reefs. DOI: 10.1007/s00338-021-02118-6.

Cheers, on behalf of all the authors,

Niklas Kornder



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