Biodiversity monitoring in rocky shores: Challenges of devising a globally applicable and cost-effective protocol

Abstract

Large-scale coastal monitoring programs that focus on long-term inter-annual and seasonal community variability are rare mostly because they are costly, logistically complex and require coordination by groups of dedicated scientists. The Marine Biodiversity Observation Network (MBON) is currently developing a regional collaboration throughout the American continent to collect biological data in coastal habitats using common methodologies and sharing best practices. The goal of this paper is to compare two survey methods with contrasting field time demands (i.e. in situ collected data vs. photoquadrats), identify the scales at which they may differ, and determine the convenience and suitability for their use in large-scale standardized biodiversity studies on rocky intertidal shores. Visual quadrat (VQ) data collected in the field was compared with data obtained from photographs of those same quadrats (PQ) digitally analyzed at three intertidal levels within two sites during four different times of the year. Analysis by site showed a seasonal effect in all shore levels and an effect of methods only at the low intertidal level at both sites. The PQ method is a reliable, cheap and time efficient tool for the long-term study of rocky intertidal communities. It is capable of detecting the spatial and temporal variability as the VQ method at various scales including tidal height, time of the year and site. We suggest the use of the mid intertidal level as the standardized sampling zone across latitudes on the basis of having higher diversity than the high intertidal, more sampling time than the low intertidal level, and being more affected by climate change both through changes in the air (temperature and wind) and in the ocean (warming and acidification). This study provides empirical evidence that a simple, low-cost and low-tech method may offer the required information that large-scale monitoring programs need.