Advances in assessing Sabellaria spinulosa reefs for ongoing monitoring

Abstract

Standardized and repeatable data acquisition and analyses are required to enable the mapping and condition monitoring of reefs within Marine Protected Areas (MPAs). Changes in habitat condition must be reliably identified and reported to best support evidence‐based management. Biogenic reefs in temperate waters, that is, hard matter created by living organisms and raised above the seabed, provide food and shelter for many plant and animal species. This article explores the feasibility of habitat mapping, using remote sensing datasets, as well as metrics for repeatable and suitable assessment of areas of Sabellaria spinulosa for their status as biogenic reef. Data were gathered within the North Norfolk Sandbanks and Saturn Reef candidate Special Area of Conservation/Site of Community Importance in the southern North Sea. Six study areas were identified as potential locations of biogenic reef using previously acquired data, and these were targeted for further investigation using a combination of high resolution multibeam echosounder and sidescan sonar. Where potential S. spinulosa was identified from the acoustic data, a drop‐down camera system was employed for visual verification. Areas of known and potential S. spinulosa reef were mapped successfully at two of the six study areas, although future approaches should take careful consideration of the seabed morphology and predominant habitat backdrop to successfully interpret such data. Camera tows from S. spinulosa reef areas were broken up into 5‐s segments, with each segment scored for (a) average tube elevation; (b) average percentage cover; and (c) for the presence or absence of S. spinulosa. These metrics were utilized to create summary statistics, including a value of patchiness derived from presence/absence data, that is recommended for application as part of future monitoring programs. The application of this methodology could benefit wider assessments of similar threated or declining habitats such as intertidal Mytilus edulis beds on mixed and sandy sediments, Maerl beds, Modioulus modiolus beds, Ostrea edulis beds, and Zostera beds where patchiness may also be considered of environmental importance.

Improving benthic biodiversity assessments in turbid aquatic environments

“…Notable differences in reef detail were present between the two methods (Figure 7). Out of the 116 images taken across Stations 7, 8, 1,5 and 16 in Swansea Bay during CLOC deployments, 67 identified reef structures of either ‘Low’ or ‘Medium’ (58%) and 49 recorded ‘No Reef’ (42%) based on Jenkins et al (2018) criteria. Out of the 47 images taken across these four stations during non‐CLOC deployments, one identified a reef structure of ‘Low’ (2%) and 46 recorded ‘No Reef’ (98%).…”

“…The visualization of S. alveolata reefs in images recorded using the CLOC was also greatly enhanced when compared with those collected during non‐CLOC deployments. These reefs are considered as being of high conservation importance and are protected under a range of national and international legislations (Gubbay, 2007; Jenkins et al, 2018). Biogenic reefs provide microhabitats for other organisms, leading to higher levels of biodiversity when compared with their surrounding environment (Jonsson et al, 2004; Limpenny et al, 2010).…”

“…Sabellaria alveolata reef assessments, where appropriate, were also undertaken for images in Swansea Bay based on the Jenkins et al (2018) and Gubbay (2007) reef score criteria (Supporting Information Data S1, Section A, Table 2). Elevation and patchiness (percentage cover) were recorded for each image where S. alveolata was deemed present to determine whether structures could be considered a reef (scored as low, medium, and high).…”

Conservation Implications of Sabellaria spinulosa Reef Patches in a Dynamic Sandy-Bottom Environment

“…In the North Sea, most reefs are located near the British coast (Fariñas-Franco et al, 2014;Gibb et al, 2014;Pearce, 2014). They are often encountered on rocky substrates (Pearce, 2014), but are also observed on sandy bottoms (Pearce et al, 2014;Jenkins et al, 2018). The worms excrete fecal matter that may increase local food availability (Pearce, 2014), while the reefs increase habitat complexity and provide refugia and settlement substrate (Hendrick and Foster-Smith, 2006;Pearce et al, 2013;van der Reijden et al, 2019).…”

Camera methods for the assessment of coastal biodiversity in low visibility environments

“…Classification success is defined as the number of investigators which similarly identified an organism fraction of the total number of investigators (n = 3). Jenkins et al (2018) from the elevation and percentage cover categories proposed by Gubbay (2007).…”