The seven sins of climate change: A review of rates of change, and quantitative impacts on ecosystems and water quality in the Great Barrier Reef.

The term climate change encompasses many types of impacts and threats to the long-term outlook of coastal marine ecosystems. Based on a structured Evidence Summary methodology, this review synthesises the peer-reviewed knowledge on climate change impacts on the Great Barrier Reef (GBR). We summarise the observed and predicted region-specific rates of change for seven climate change factors; three representing episodic extreme weather events (heatwaves, tropical storms, and extreme rainfall events), and four chronic progressive climate change factors (rising temperatures, ocean acidification and sea level, and altered cloudiness/windiness).

Assessing the risk of light reduction from natural sediment resuspension events and dredging activities in an inshore turbid reef environment.

The reduction in benthic light from natural sediment resuspension events, dredging activities and clouds was quantified over multiple time periods (days to weeks) from a 3-year in-situ field study in the inshore turbid-zone coral communities of the Great Barrier Reef. The results were then used to examine the tolerance levels of three coral species and a sponge to light reduction and associated changes in spectral light quality (in conjunction with elevated sediment concentrations) in a 28-day laboratory-based study. All species survived the exposures but sub-lethal responses involving changes in pigmentation, lipids and lipid ratios were observed.

Sediment tolerance mechanisms identified in sponges using advanced imaging techniques.

Terrestrial runoff, resuspension events and dredging can affect filter-feeding sponges by elevating the concentration of suspended sediments, reducing light intensity, and smothering sponges with sediments. To investigate how sponges respond to pressures associated with increased sediment loads, the abundant and widely distributed Indo-Pacific species was exposed to elevated suspended sediment concentrations, sediment deposition, and light attenuation for 48 h (acute exposure) and 4 weeks (chronic exposure). In order to visualise the response mechanisms, sponge tissue was examined by 3D X-ray microscopy and scanning electron microscopy (SEM).

The sponge microbiome project.

Marine sponges (phylum Porifera) are a diverse, phylogenetically deep-branching clade known for forming intimate partnerships with complex communities of microorganisms. To date, 16S rRNA gene sequencing studies have largely utilised different extraction and amplification methodologies to target the microbial communities of a limited number of sponge species, severely limiting comparative analyses of sponge microbial diversity and structure. Here, we provide an extensive and standardised dataset that will facilitate sponge microbiome comparisons across large spatial, temporal, and environmental scales.

Effects of sediment smothering on the sponge holobiont with implications for dredging management.

One of the ways dredging can affect benthic habitats is through high levels of sediment deposition, which has the potential to smother sessile organisms such as sponges. In order to provide pressure-response values to sedimentation and tease apart the different cause-effect pathways of high turbidity, 5 sponge species, including heterotrophic and phototrophic nutritional modes, were exposed for up to 30 d to multiple sediment deposition events, each of which resulted in an initial covering of 80-100% of the surface of the sponges in a layer ~0.5 mm thick.

Effects of combined dredging-related stressors on sponges: a laboratory approach using realistic scenarios.

Dredging can cause increased suspended sediment concentrations (SSCs), light attenuation and sedimentation in marine communities. In order to determine the combined effects of dredging-related pressures on adult sponges, three species spanning different nutritional modes and morphologies were exposed to 5 treatment levels representing realistic dredging scenarios. Most sponges survived under low to moderate turbidity scenarios (SSCs of ≤ 33 mg L, and a daily light integral of ≥0.

Effects of suspended sediments on the sponge holobiont with implications for dredging management.

Dredging can cause high suspended sediment concentrations (SSC) in the water column, posing a hazard to filter feeding organisms like sponges as sediment may clog their aquiferous systems and reduce feeding. In order to provide pressure-response values for sponges to SSC and tease apart the cause:effect pathways of dredging pressures, five heterotrophic and phototrophic species were experimentally exposed to a range of dredging-relevant SSC of up to 100 mg L, with light compensation across treatments to ensure that SSC was the primary physical parameter. This study shows that some sponge species exposed to high SSC (≥23 mg L) for extended periods (28 d) have lower survival, increased necrosis and depletion of energy reserves.

Microbiome analysis of a disease affecting the deep-sea sponge Geodia barretti.

Reports of sponge disease are becoming increasingly frequent, although almost all instances involve shallow-water, tropical species. Here, we describe the first disease affecting the deep-water sponge, Geodia barretti. The disease is characterised by brown/black discolouration of the sponge tissue, extensive levels of tissue disintegration and increased levels of fouling.

Using a thermistor flowmeter with attached video camera for monitoring sponge excurrent speed and oscular behaviour.

A digital, four-channel thermistor flowmeter integrated with time-lapse cameras was developed as an experimental tool for measuring pumping rates in marine sponges, particularly those with small excurrent openings (oscula). Combining flowmeters with time-lapse imagery yielded valuable insights into the contractile behaviour of oscula in . Osculum cross-sectional area (OSA) was positively correlated to measured excurrent speeds (ES), indicating that sponge pumping and osculum contraction are coordinated behaviours.

Effects of light attenuation on the sponge holobiont- implications for dredging management.

Dredging and natural sediment resuspension events can cause high levels of turbidity, reducing the amount of light available for photosynthetic benthic biota. To determine how marine sponges respond to light attenuation, five species were experimentally exposed to a range of light treatments. Tolerance thresholds and capacity for recovery varied markedly amongst species.

Stochasticity in space, persistence in time: genetic heterogeneity in harbour populations of the introduced ascidian Styela plicata.

Spatio-temporal changes in genetic structure among populations provide crucial information on the dynamics of secondary spread for introduced marine species. However, temporal components have rarely been taken into consideration when studying the population genetics of non-indigenous species. This study analysed the genetic structure of Styela plicata, a solitary ascidian introduced in harbours and marinas of tropical and temperate waters, across spatial and temporal scales.

Down under the tunic: bacterial biodiversity hotspots and widespread ammonia-oxidizing archaea in coral reef ascidians.

Ascidians are ecologically important components of marine ecosystems yet the ascidian microbiota remains largely unexplored beyond a few model species. We used 16S rRNA gene tag pyrosequencing to provide a comprehensive characterization of microbial symbionts in the tunic of 42 Great Barrier Reef ascidian samples representing 25 species. Results revealed high bacterial biodiversity (3 217 unique operational taxonomic units (OTU0.

Stress levels over time in the introduced ascidian Styela plicata: the effects of temperature and salinity variations on hsp70 gene expression.

Species distribution, abundance, and long-term survival are determined by biotic and abiotic regimes. However, little is known about the importance of these factors in species range expansion. Styela plicata is a solitary ascidian introduced all over the world by ship fouling, including salt marsh habitats, where introduced populations must tolerate high seasonal variations in temperature and salinity.

The whereabouts of an ancient wanderer: global phylogeography of the solitary ascidian Styela plicata.

Genetic tools have greatly aided in tracing the sources and colonization history of introduced species. However, recurrent introductions and repeated shuffling of populations may have blurred some of the genetic signals left by ancient introductions. Styela plicata is a solitary ascidian distributed worldwide.