Description
Subtidal macrobenthos was sampled in the Tsitsikamma National Park between 2009 and 2012 to compare shallow (11–25 m) and deep (45–75 m) sites. The resultant records of sampling events, photographic images of the sea floor, and invertebrate and algal species occurrences constitute this dataset. See Heyns et al. (2016). The following classes of data are represented. DwC Event Core: A parent sampling event represents a sample station in which 30 child sampling events / photoquadrats were randomly selected. There are 6 sample stations / parent events (i.e. 180 child sampling events / photoquadrats) for the deep site and 6 parent events (180 child sampling events / photoquadrats) for the shallow site. A 0.2m^2 photoquadrat on each photo was sampled using Coral Point Count for Excel, using 54 random points. DwC Occurrence Extension: An occurrence record represents the percentage cover of a species calculated from the 54 random points falling in the 0.2m^2 photoquadrat (i.e. the individual species points from each photoquadrat have not been published). DwC Extended Measurement or Fact Extension: Each record represents the percentage cover, in the 0.2m^2 photoquadrat, of the following elements (either Tape/Wand/Shadow), abiotic features (e.g. shells, substrate) or biodiversity that could not be identified, even at a high level. DwC Audubon Media Description: Each record represents the digital photograph containing the 0.2m^2 photoquadrat.
Data Records
The data in this sampling event resource has been published as a Darwin Core Archive (DwC-A), which is a standardized format for sharing biodiversity data as a set of one or more data tables. The core data table contains 372 records.
3 extension data tables also exist. An extension record supplies extra information about a core record. The number of records in each extension data table is illustrated below.
This IPT archives the data and thus serves as the data repository. The data and resource metadata are available for download in the downloads section. The versions table lists other versions of the resource that have been made publicly available and allows tracking changes made to the resource over time.
Versions
The table below shows only published versions of the resource that are publicly accessible.
How to cite
Researchers should cite this work as follows:
Heyns-Veale E (2019): Distribution patterns of subtidal macrobenthos in the Tsitsikamma National Park. v1.8. The South African Institute for Aquatic Biodiversity. Dataset/Samplingevent. http://ipt.saiab.ac.za/resource?r=tsitsikamma&v=1.8
Rights
Researchers should respect the following rights statement:
The publisher and rights holder of this work is The South African Institute for Aquatic Biodiversity. This work is licensed under a Creative Commons Attribution (CC-BY 4.0) License.
GBIF Registration
This resource has been registered with GBIF, and assigned the following GBIF UUID: 96f53e46-902a-48d5-a599-7c96c065b214. The South African Institute for Aquatic Biodiversity publishes this resource, and is itself registered in GBIF as a data publisher endorsed by South African Biodiversity Information Facility.
Keywords
macrobenthic communities; fish habitat; warm-temperate reefs; photoquadrats; Occurrence
Contacts
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http://orcid.org/https://orcid.org/0000-0001-8208-7610
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Geographic Coverage
Photoquadrats were collected just offshore from the Storms River mouth, inside the Tsitsikamma National Park marine protected area, South Africa, between 11 - 25 and 45 - 75 m depth.
| Bounding Coordinates | South West [-34.04, 23.892], North East [-34.023, 23.924] |
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Taxonomic Coverage
Marine macrobenthos identifiable from photoquadrats
| Phylum | Bryozoa, Brachiopoda (Lampshells), Echinodermata (Echinoderms), Porifera (Sponges) |
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| Subphylum | Tunicata (Acsidians) |
| Class | Anthozoa, Hydrozoa (Hydroids), Gastropoda, Florideophyceae (Red algae) |
| Family | Codiaceae (Green algae), Dictyotaceae (Brown algae) |
Temporal Coverage
| Start Date / End Date | 2009-07-19 / 2012-07-25 |
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Project Data
Effective marine resource management requires knowledge of the distribution of critical habitats that support resource populations and the processes that maintain them. Reefs that host diverse macrobenthic communities are important habitats for fish. However, detailed information on macrobenthic communities is rarely available and is usually limited to SCUBA diving depths. To establish depth-related distribution patterns and drivers that structure reef communities, the macrobenthos situated in a warm-temperate marine protected area (MPA; 34°01′24S; 23°54′09E) was sampled between 2009 and 2012. Comparison of shallow (11–25 m) and deep (45–75 m) sites revealed significantly different communities, sharing only 27.9 % of species. LINKTREE analysis revealed a changeover of species along the depth gradient, resulting in four significantly different assemblage clusters, each associated with particular environmental variables. High light intensity supported benthic algae at shallow depths, and as light availability decreased with depth, algal cover diminished and was eventually absent from the deep reef. Upright growth forms and settled particulate matter were positively related to depth and dominated the deep reef. Reduced wave action and currents on the deep reef can explain the increased settling of suspended particles. Under such conditions, clogging of feeding parts of the encrusting species is expected, and upright growth would be favoured. Considering that most MPAs are restricted to shallow coastal habitats and that macrobenthic communities change significantly with depth, it is probable that many unique deep reef habitats are currently afforded no protection.
| Title | Depth-related distribution patterns of subtidal macrobenthos in a well-established marine protected area |
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| Funding | Funding for this project was provided by the National Research Foundation of South Africa, the Elwandle Node of the South African Environmental Observation Network, the South African Institute for Aquatic Biodiversity, the African Coelacanth Ecosystem Programme and the British Ecological Society. |
| Study Area Description | The research was conducted in the Tsitsikamma National Park (TNP) MPA, which is one of Africa’s oldest (established in 1964) and largest (360 km2) no-take MPAs. The TNP MPA is situated in the middle of the warm-temperate Agulhas Ecoregion. It protects a 60-km stretch of coastline and extends 5 km offshore to a depth of approximately 100 m. The geology comprises steeply sloped quartzitic sandstone beds that lie parallel to the coastline. Subtidally, these rocky formations form a series of parallel reef ridges separated by valleys filled with fine-grained sand. Sampling was conducted at shallow (11–25 m) and deep (45–75 m) reef sites situated in the middle of the TNP MPA. Both the shallow (area: 1.8 km2) and deep (area: 3.15 km2) sites included large expanses of solid high- and low-profile reefs. The reef sites represent some of the best examples of pre-exploitation subtidal communities in South Africa. |
| Design Description | Our aims were to characterize the species composition and distribution of the macrobenthos and identify the processes that might be responsible for any differences between shallow (11–25 m) and deep (45–75 m) nearshore reefs. |
The personnel involved in the project:
Sampling Methods
Prior to sampling, both reef sites were bathymetrically mapped with a GPS-linked echo sounder and a 300 × 300 m grid was overlaid on the mapped sites. Each grid was classified according to profile (high or low), and sampling followed a stratified random approach, with even allocation of sampling effort between reef sites and high and low profile reefs.
| Study Extent | The shallow reef site (11 - 25 m) was situated just east of the Storms River mouth (-34.0198, 23.9034) and the deep reef site (45 - 75 m) was about 1 km south west of the Storms River mouth. |
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Method step description:
- Assemblage composition The species compositions of the macrobenthic assemblages were determined by estimating percentage cover from photoquadrats collected at six sample stations within each reef site. Photoquadrats on the shallow reef site were obtained by SCUBA divers. From the midpoint of each station, divers swam 25 meters in eight predefined directions. Eight to ten photographs were then haphazardly taken around the 25-m distance mark using a Canon G9 camera (12.1 meg- apixels) mounted on a tripod. The tripod setup maintained a set distance from the substrate and sampled an area of ca. 0.33 m2. On the deep reef, photoquadrats were obtained with a ROV (Falcon Seaeye: 12177) fitted with a 1Cam (SubC Control; 12.3 megapixel HD camera). The 1Cam, which could be orientated to capture benthic images at a 90° angle, was fitted with two laser pointers, thus permitting size approximation of the sampled area. Due to strong currents and restricted maneuverability, sampling at each deep reef station was conducted along a single 100-m transect, in contrast to the method employed at the shallow reef site. Along each transect, the ROV captured between 100 and 150 photoquadrats within 2 m of either side of the transect line. Thirty photographs were selected randomly from each sample station, amounting to 180 photoquadrats per reef site. Photoquadrats were calibrated in Coral Point Count with Excel extensions (CPCe 4.1) and 56 × 31 cm (0.2 m2) blocks were superimposed onto individual images. A species accumulation curve was plotted to estimate the number of points required to identify 95 % of the macrobenthic species per photoquadrat, which indicated that 54 points were required. Under each point, individuals or colonies were identified to the nearest taxon (noting substrate cover where applicable). Environmental variables During November 2011 and February 2012, light intensity (photosynthetically active radiation; 400–700 nm) was measured at three randomly selected sample stations from both the shallow and deep reef sites. Light intensity measurements were taken by employing a LICOR LI-193 Spherical Quantum Sensor. Temperature data were recorded by divers on the shallow reef, and a temperature probe (Onset HOBO Pro v2) was attached to the ROV to obtain temperature data when deep reef photoquadrats were collected. Reef profiles for each sampling station were estimated by divers on the shallow reef and from the ROV footage on the deep reef. The overlay from the ROV provided accurate depth measurements and allowed for estimates of the deep reef profile. Substrate type was estimated as percentage cover obtained from the photoquadrats. Depth was recorded by divers at the beginning and end of each transect. Care was taken to follow a depth contour when conducting all transects with the ROV, thereby standardizing depth during sampling. To summarize, data for temperature, reef profile, depth and substrate type were collected from at each sampling station. In contrast, light intensities were extrapolated according to station depth, from light profiles constructed from data collected during two seasons from three stations per reef, as indicated above.
Additional Metadata
| Alternative Identifiers | 96f53e46-902a-48d5-a599-7c96c065b214 |
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| http://ipt.saiab.ac.za/resource?r=tsitsikamma |