Macroalgal species richness and assemblage composition of the Great Barrier Reef seabed

Understanding the drivers of broad-scale patterns of biodiversity is an overarching goal in ecology. We analysed environmental drivers of macroalgal species richness and composition on the continental shelf seabed of Australia's Great Barrier Reef (GBR), and mapped these patterns to show phycologically diverse and depauperate areas. Although shelf seabed habitats constitute similar to 61% of the GBR Marine Park area, previous floristic studies have been largely confined to intertidal and coral reef areas. Recognising the lack of knowledge of this habitat, the GBR Seabed Biodiversity Project (SBP) surveyed environmental variables and associated biodiversity across the shelf. We used SBP data for 1195 epibenthic sled sites, of which 639 sites recorded 370 macroalgal taxa, including 250 taxa not previously described in the GBR. Regression Random Forests were used to identify the environmental variables that most influence algal richness. Patterns of species composition, or assemblages, were investigated using partitioning around medoids (pam) clustering, and classification Random Forests identified the environmental variables most influential, and shapes of responses, for each assemblage. The 5 assemblages were distinguished based on taxonomy, dominant species, functional form or abundance and species richness. Overall, sediment grain size composition and light availability had the greatest influence on species richness and assemblages, with strong thresholds at 20% mud and at relative benthic irradiance of similar to 0.06 (equivalent to PAR approximate to 120 mu mol m(-2) s(-1)). This study is the first systematic analysis of the macroalgal communities of the GBR shelf seabed, providing valuable information to stimulate future research on taxonomy, productivity and ecosystem services of this habitat

Data from: Age and area predict patterns of species richness in pumice rafts contingent on oceanic climatic zone encountered

The Theory of Island Biogeography predicts that area and age explain species richness patterns (or alpha diversity) in insular habitats. Using a unique natural phenomenon, pumice rafting, we measured the influence of area, age and oceanic climate on patterns of species richness. Pumice rafts are formed simultaneously when submarine volcanoes erupt, the pumice clasts break-up irregularly, forming irregularly shaped pumice stones which while floating through the ocean are colonised by marine biota. We analyse two eruption events and more than 5000 pumice clasts collected from 29 sites and three climatic zones. Overall the older and larger pumice clasts held more species. Pumice clasts arriving in tropical and subtropical climates showed this same trend, where in temperate locations species richness (alpha diversity) increased with area but decreased with age. Beta diversity analysis of the communities forming on pumice clasts that arrived in different climatic zones showed that tropical and subtropical clasts transported similar communities while species composition on temperate clasts differed significantly from both tropical and subtropical arrivals. Using these thousands of insular habitats, we find strong evidence that area and age but also climatic conditions predict the fundamental dynamics of species richness colonising pumice clasts

Combined_data_Home_and_Havre_Dryad_Eleanor_Velasquez_6_3_18

This file contains data collected on the presence of marine invertebrates attached to floating pumice which washed ashore on the east coast of Australia and islands in the Pacific. This occurred following two marine volcano eruption events. The Home reef eruption occurred in 2006 and the Havre in 2012. Both events were used so that we could compare and contrast the differences and similarities between the two

ANOSIM results.

<p>Global R statistics and P-values in brackets, with results of pairwise tests of significance depending on collection/arrival time for response variables of species presence and absence, and species abundance listed separately.</p

Significant pumice rafting events over the last 200 years.

<p>Volcanic eruption locations, eruption dates and general trajectory paths of pumice rafts are shown illustrating the global scale and frequency of such events. To maintain figure clarity, only pumice raft-producing eruptions for the last 50 years from the Tonga-Kermadec arc, (southwest Pacific) are listed. Data sources are given in Supporting Information (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040583#pone.0040583.s002" target="_blank">Appendix S1</a>) to this paper. Base map is from Amante and Eakins <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040583#pone.0040583-Amante1" target="_blank">[14]</a>.</p

Epibiont distribution on Home Reef pumice.

<p>(<b>A</b>) Three pumice clasts collected from Broadbeach on December 27, 2007 with well-developed biological keels of the anemone <i>Calliactus</i> sp. with cheilostome Bryozoa (<i>Jellyella</i> sp.) along the waterline and <i>Rivularia</i> spp. occupying all of the dorsal surface with occasional goose barnacles (<i>Lepas anserifera</i>); pumice clast at left is 5 cm long. (<b>B</b>) Typical observed polarity in epibiont distribution on pumice with dorsal surfaces almost exclusively occupied by cyanobacteria (<i>Rivularia</i> sp.), and here, the ventral surface entirely covered by cheilostome Bryozoa (<i>Jellyella</i> sp.) colonies. Clast is 1.7 cm long, collected from Lamberts Beach, Mackay.</p

Quantitative data for epibionts transported by the 2006–2007 pumice rafts.

<p>The number of individuals is based on descriptions of 4984 clasts collected from locations listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040583#pone-0040583-t001" target="_blank">Table 1</a>.</p

Quantitative data for colonial epibionts transported by the 2006–2007 pumice rafts.

<p>Areal coverage is based on descriptions of 4984 clasts collected from locations listed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0040583#pone-0040583-t001" target="_blank">Table 1</a>.</p

Proportions of rafted epibionts along the trajectory.

<p>Number refers to number of taxonomic units identified at each sample site. Marine invertebrates are grouped in terms of feeding behaviours. Suspension and filter feeders (e.g., cheilostome Bryozoa, goose barnacles, hydroids/scyphozoans, serpulids, corals, molluscs, and oysters) show significant early recruitment (Tonga) with epibiont diversity generally maintained along the raft trajectory. The numbers of plants (cyanobacteria, macroalgae and calcareous algae) increased with time and along the trajectory, particularly once pumice had arrived into eastern Australian waters. Overall, epibiont diversity increased with time. Bar graphs are colour-coded with respect to observation/collection timing: purple, February 2007; blue, April-May 2007 and; green, December 2007. <i>N</i> is total number of species/taxonomic units observed, and <i>n</i> is number of pumice clasts described from each location. Abbreviations: Ph, photosynthetic; S & FF, suspension & filter feeders; G & B, grazers & borers; P & S, predators and scavengers. Locations: MR, Marion Reef; MA, Mackay; LM, Lady Musgrave; BR, Broadbeach; BB, Byron Bay; BA, Ballina. Tonga sample site occurs ∼2900 km to the east. Base map from Google Earth.</p

Pumice strand sample sites, Eastern Australia.

<p>Pumice strand sample sites, Eastern Australia.</p