SE_BrazilRockyShores

Study Extent

Southern most site (Cibratel) was located in São Paulo state (24.20088 S, 46.81024 W) and the northernmost site (Forno/Búzios) in Rio de Janeiro (22.76273 S, 41.87503 W). Sites were selected following a nested hierarchical design including variability at scales of (i) regions (100s of kilometres), (ii) sub-regions (10s of kilometres), sites (kilometres) and quadrats (metres to 10s of metres). Biological data were haphazardly sampled in the intertidal zone along an area of approximately 100 m horizontal distance during low tide periods of spring tides.

Sampling

In each site, sessile and motile macrobenthic organisms were assessed from the lower limit of the sublittoral fringe, just above the Sargassum spp. cover, to the upper limit of the low midlittoral, i.e., below the zone of prevailing cover of the barnacle Chthamalus bisinuatus, divided in three tidal zones: (i) infralittoral fringe, (ii) lower midlittoral, and (iii) mid midlittoral (as in Christofoletti et al., 2011 and Pardal-Souza et al., 2017). A section of shore of approximately 100 m horizontal length was selected at each site. Filter feeders (mussel Mytilaster solisianus, barnacles Tetraclita stalactifera and C. bisinuatus), a predatory gastropod (whelk Stramonita haemastoma) and grazers (limpets Lottia subrugosa and Fissurela rosea, and periwinkle Echinolittorina lineolata) were sampled through images, scraping or by manual collection in the meso and supralittoral of each location. All sampling was conducted by placing sampling units in the mid portion of each stratum dominated by characteristic species, as follows: E. lineolata at the supralittoral; C. bisinuatus at the upper midlittoral; M. solisianus at the mid midlittoral; T. stalactifera, L. subrugosa and F. rosea at the lower midlittoral. The density and size of the barnacles T. stalactifera and the limpets L. subrugosa and F. rosea was measured from fifteen squared images of 100 cm², while the same parameters were measured for C. bisinuatus in 25 cm2 images. All limpets and, at least 15 randomly selected individuals of barnacles, were measured from each image. The abundance of the mussel M. solisianus was estimated as percentage cover in photos of 625 cm² (n = 10) using a 100 regular intersection grid. In laboratory, mussels scraped from 10 x 10 cm parcels in each location were photographed for measuring, and then weighted. Total abundance of the whelk S. haemastoma per site was estimated collecting specimens in quadrats of 625 cm² (n = 20), and periwinkles E. lineolata were accessed by one person picking specimens by hand for five minutes. All collected individuals were after measured in laboratory, either from directly using a caliper (S. haemastoma) or in images (all other), where the largest length of shell and operculum were the representative measure of size for mollusks and the barnacles, respectively.

Quality Control

Taxonomic validity was verified using the World Register of Marine Species (WoRMS; www.marinespecies.org) and the Ocean Biogeographic Information System (OBIS; https://obis.org/)

Method steps

1. All sampling procedures were repeated at each site.

Species investigated includes filter feeders (mussel Mytilaster solisianus, barnacles Tetraclita stalactifera and Chthamalus bisinuatus), a predatory gastropod (whelk Stramonita haemastoma) and grazers (limpets Lottia subrugosa and Fissurela rosea, and periwinkle Echinolittorina lineolata).

1. Mytilaster solisianus
   rank: species
2. Tetraclita stalactifera
   rank: species
3. Chthamalus bisinuatus
   rank: species
4. Stramonita haemastoma
   rank: species
5. Lottia subrugosa
   rank: species
6. Echinolittorina lineolata
   rank: species

Between April and September 2015, a descriptive survey was carried out on 62 rocky shores along the Southeast coast of Brazil, comprising a linear length of approximately, 530 km. The whole region studied is dominated by a microtidal regime, with mean sea level around 0.7 m and tidal range of about 1.4 m. Locations were selected within six main regions with distinct natural conditions and anthropogenic influence: (i) Baixada Santista, (ii) São Sebastião Channel, (iii) Ubatuba, (iv) Green Coast, (v) Rio de Janeiro, and (vi) Lakes. Details of each region can be found in Pardal et al. (2021), but briefly, Baixada Santista and Rio de Janeiro are, consequently, the metropolitan regions of São Paulo and Rio de Janeiro cities, which concentrate the largest anthropically influenced sites due to higher degree of urbanization of the two most populated cities in Brazil. The Ubatuba region and Green Coast have the least populated areas and largest freshwater discharges, while São Sebastião Channel and Lakes are highly touristic but with an intermediate level of anthropic influence when comparing to the other regions sampled here. There are also gradients in temperature and productivity along the studied regions, where colder waters are found towards the north due to upwelling events in the Lakes subregion, and higher productivity is commonly found associated with large bays in Baixada Santista and Rio de Janeiro. Sites were selected following a nested hierarchical design including variability at scales of (i) regions (100s of kilometres), (ii) sub-regions (10s of kilometres), sites (kilometres) and quadrats (metres to 10s of metres). Biological data were haphazardly sampled in the intertidal zone along an area of approximately 100 m horizontal distance during low tide periods of spring tides.