Ben G. Holt (1,2) & Rodolfo Rioja-Nieto (2,3) & M. Aaron MacNeil (4) & Jan Lupton (2) & Carsten Rahbek (1)
1 Department of Biology, Center for Macroecology, Evolution and Climate, University of Copenhagen, Universitetsparken 15,Copenhagen DK-2100, Denmark;
2 Centre forMarine Resource Studies, School for Field Studies, 1West Street, South Caicos,
Turks and Caicos Islands, BritishWest Indies
3 Facultad de Ciencias, Unidad Multidisciplinaria de Docencia e Investigacion –Sisal, Universidad Nacional Autonomade Mexico, Puerto de Abrigo s/n Hunucma, Sisal 97355,Mexico
4Australian Institute of Marine Science, PMB3 Townsville MC, Townsville, Qld 4810, Australia
- In light of the continuing biodiversity crisis, the need for high-resolution, broad-scale ecological data is particularly acute. The expansive scale of volunteer data collection programmes provides an opportunity to address this challenge, however, protocols used to collect such data are typically less standardized than those used by professional scientists. Although previous studies have established that different protocols can lead to different results, it remains unclear how relevant these differences are to specific study goals, such as biodiversity assessment.
- This study uses both null model and Bayesian occupancy approaches to examine the capacity of a widely used volunteer survey protocol, the roving diver transect, to detect patterns of marine fish diversity.Richness estimates are compared with those obtained using the conventional belt transects favoured in many peer reviewed studies, examining the power of both protocols to detect statistically significant differences between survey sites and quantifying differences in detectability.
- Pairwise site comparisons of a-diversity (i.e. within site diversity) were consistent between protocols, particularly for species totals.
- The roving diver transect protocol detected a substantially larger number of species than the belt transect protocol, due to notably higher detectability, even after controlling for confounding factors. Both protocols detected the same species pool, although the species richness among observations was higher for the belt protocol at certain sites.
- The significance of pairwise site b-diversity (i.e. differentiation between sites) comparisons differed between the protocols and care should be exercised, when using either protocol, when studying variation in species composition.
- These results provide vital information for managers and researchers considering the use of volunteer data or protocols for the purpose of biodiversity assessment in aquatic systems, helping to quantify the value of thousands of existing survey records. The larger number of species detected by the volunteer protocol suggests this protocol may be advantageous with regards to the completion of taxonomic lists.
- Key-words: conservation, coral reef, null models, Reef Environmental Education Foundation,
roving diver transect, SCUBA, species density, underwater visual census
One of the most important challenges for biologists is to describe and explain geographical patterns in biodiversity. Analysis of such patterns provides insight into the ecological and evolutionary processes that shape life on earth, and is also a prerequisite for conservation prioritization. Research into large-scale diversity patterns has traditionally focused on taxonomic groups for which large amounts of distributional data are available, such as birds, mammals and butterflies, with many of these systems benefitting from volunteer data collection (e.g. Robbins et al. 1989; Greatorex-Davies & Roy 2000; Newman, Buesching & Macdonald 2003). The value of volunteer schemes with regards to biodiversity monitoring has been considered for these systems, with mixed results (Lovell et al. 2009; Schmeller et al. 2009; Kremen,Ullmann & Thorp 2011).
There is an urgent need to expand the taxonomic, temporal and spatial scale of applied and theoretical biodiversity research, particularly within less accessible environments such as aquatic systems. Paradoxically, some volunteer data collection schemes have been highly successful in these environments with regards to the quantity of data collected (e.g. Pattengill-Semmens & Semmens 2003; Goffredo et al. 2010). If these data are shown to be suitable for the study of patterns of diversity, the value of such schemes will hugely increase, with implications for the collection of data in all ecosystems.
A key aspect relating to the value of volunteer data is the reliability of data returned from the protocols used to collect it. For studies performed by professional scientists, underwater visual survey protocols are often designed to minimize bias, maximize precision and ensure repeatability. Due to logistical limitations, vast sections of the world’s aquatic ecosystems are rarely, or never, surveyed by professional scientists. The large pool of volunteer enthusiasts has potential to substantially augment the census capabilities of professional researchers. For example, over 8,000 surveys were performed worldwide during 2011 alone by one volunteer organization (R.E.E.F. 2012). Protocols designed for volunteers also attempt to standardize survey efforts, but must balance this requirement against the need to maintain the interest of the public. Whether data produced by such protocols are suitable for comparative studies of biological diversity remains unclear.
The development and popularity of underwater visual survey techniques using self-contained underwater breathing apparatus (SCUBA) equipment has resulted in monitoring of the underwater environment on a scale that was previously impossible. Underwater visual survey methods have been used extensively in tropical (e.g. Pattengill-Semmens & Semmens 2003) and temperate marine habitats (e.g. Goffredo et al. 2010), as well as freshwater systems (e.g. Brosse et al. 2001). Many previous studies have compared underwater visual survey protocols; most of these studies focused on identifying sources of bias within methods, often with a view to quantifying differences among protocol (e.g. Thresher & Gunn 1986; St John, Russ & Gladstone 1990; Sullivan & Chiappone 1992; Miller & Ambrose 2000; Schmitt, Sluka & Sullivan-Sealey 2002). Few, if any, of these studies have been focused on the capacity for underwater visual survey protocols to reflect actual biological patterns or to test specific ecological hypotheses. This is surprising, as it is widely acknowledged that decisions regarding the choice of methodology should be based on the study question. The likely reason for this discrepancy is that in many underwater ecosystems it is impossible to completely sample any area using any method and, without a full taxonomic list for comparison, it is difficult to quantify the performance of any particular sampling method.
Our study addresses this issue by concentrating large amounts of survey effort on a very small number of sites (three) to both reliably identify any differences between two test protocols and thoroughly elucidate patterns among study sites. The techniques chosen for this study represent the most frequently used underwater visual survey methodology in published peer reviewed fish diversity studies (the belt transect) and the Roving Diver Technique (RDT) used by the Reef Environmental Education Foundation (REEF) volunteer fish survey project (Pattengill-Semmens & Semmens 2003), thought to be the largest marine species sighting database in the world, and similar to protocols used by other successful programmes. Volunteer data, such as those collected by REEF, are potentially a highly valuableresource for the marine environment, where the measurement of fundamental aspects of diversity, across expansive spatial scales, has been suggested to be a key management priority (Palumbi et al. 2008). Although studies typically vary considerably on the specific aspects of diversity they address, e.g. taxonomical relatedness (Carranza, Defeo & Arim 2011), phylogenetic diversity, functional diversity (Halpern & Floeter 2008), species diversity and community composition comparisons (i.e. a and b-diversity) are relevant to most studies and conservation objectives, and are therefore the focus of this study. As belt transects are regularly used in professional reef fish diversity studies (Kulbicki et al. 2010), they represent a logical choice with which to compare the performance of the RDT protocol. The extent to which belt transect results are consistent to those produced using RDT protocols is therefore informative regarding the utility of vast amounts of volunteer data that are currently available and collected in the future. The objective of this study is to determine whether the two protocols differ in terms of the a (i.e. within site diversity) and b-diversity (i.e. differentiation between sites) of the communities they record and in their power to detect significant differences in these biodiversity measures between these communities.
We also examine how detectability (i.e. probability to detect a species that is present in a surveyed area at the time of survey) varies between protocols, as well variation associated with sites, functional groups, taxonomic groups, survey duration and underwater visibility.