Importance of philopatry and hydrodynamics in the recruitment of bioeroding sponges on Indonesian coral reefs

2019 ◽  
Vol 70 (6) ◽  
pp. 755
Author(s):  
Joseph Marlow ◽  
Abdul Haris ◽  
James Bell
Keyword(s):  
Coral Reefs ◽  
Large Scale ◽  
Species Assemblage ◽  
Coral Mortality ◽  
Factors Affecting ◽  
Larval Recruitment ◽  
Spatial Coverage ◽  
Reef Degradation ◽  
Adult Abundance ◽  
Cliona Orientalis

Increasingly frequent large-scale coral mortality events are occurring across the globe, leading to a rise in available reef substrata and promoting an increase in the abundance of other benthic taxa. One such group are bioeroding sponges, which can benefit considerably from reef degradation. However, the occupation of new substrates is partially reliant upon larval recruitment, and currently little is known about the factors affecting bioeroding sponge recruitment. In this study we investigated the potential drivers of bioeroding sponge recruitment using a 2-year deployment of experimental calcareous substrates across seven reefs in the Wakatobi region of Indonesia. Recruitment was observed for five bioeroding sponge species, namely Cliona orientalis, Cliothosa cf. aurivillii, Cliothosa hancocki and two presently unidentified brown clionaids, Cliona aff. viridis sp. A and Cliona aff. viridis sp. B. Recruits were present on 69% of the experimental substrates but had a low mean (±s.e.m.) spatial coverage of just 0.42±0.13%. Total recruitment and species assemblage structure were correlated with local adult abundance, water flow and substrate cues. Our results suggest that any proliferation of bioeroding sponges on newly available substrate following coral mortality is likely to be conditional on local adult abundance and hydrodynamics.

scholarly journals Sponge bioerosion and habitat degradation on Indonesian coral reefs

2021 ◽  
Author(s):  
◽  
Joseph Marlow
Keyword(s):  
Coral Reefs ◽  
Habitat Degradation ◽  
Sponge Species ◽  
Environmental Drivers ◽  
Light Limitation ◽  
Sponge Tissue ◽  
Assemblage Composition ◽  
Larval Recruitment ◽  
Reef Degradation ◽  
The Common

<p>Coral reefs are among the most diverse ecosystems on the planet, yet they are also sensitive to anthropogenic disturbances that can degrade these systems. On many degraded reefs, large increases in bioeroding sponge abundance have occurred. On healthy reefs these sponges contribute to species diversity and habitat complexity, however there is growing concern that their proliferation on degraded reefs could lead to a state of net-erosion. In the Southeast Asian Indo-Pacific, the ecology of bioeroding sponges in relation to coral degradation has been poorly studied compared to other coral reef regions. This thesis aims to increase our understanding of the ecology of these sponges in the Wakatobi region of Indonesia, and their likely trajectory if reefs continue to degrade in the region.  My first research chapter aimed to identify the common bioeroding sponge species of the Wakatobi. This was achieved through in-water surveys, and subsequent spicule and phylogenetic analysis. This resulted in the identification of eight commonly occurring Wakatobi bioeroding sponge species, two of which are described for the first time. The assemblage composition was distinctly different from the only other bioeroding sponge study in Indonesian waters (Calcinai et al. 2005), highlighting the need for more clionaid taxonomic information from the region.  Having identified the common bioeroding sponge species in the region, my second chapter assessed the major environmental drivers of the abundance and assemblage composition of these sponges. Abundance surveys were conducted at 11 reef sites characterised by different environmental conditions and states of reef health. Bioeroding sponges occupied 8.9% of suitable substrate, and differences in abundance and assemblage composition were primarily attributed to differences in the availability of dead substrate. However, abundance was lowest at a sedimented and turbid reef, despite abundant dead substrate availability. This indicates a limited resilience in some species to conditions associated with terrestrial run-off and that not all forms of reef degradation are beneficial for bioeroding sponges. The capacity to increase spatial occupation of degraded reefs is also dependent upon larval recruitment and my third chapter was a two year recruitment study using in situ experimental calcareous blocks. Recruitment occurred rapidly and consistently with bioeroding sponges recruiting to approximately 70% of experimental blocks and exhibiting a preference for settlement on uncolonised dead calcareous substrates. The importance of substrate settlement cues and extent of larval dispersal appeared to differ between species, indicative of different recruitment mechanisms. Any significant increase in the availability of exposed calcareous substrate (e.g. following a mass coral bleaching event) is therefore likely to result in widespread increases in bioeroding sponge recruitment.  Surveys conducted in my second research chapter revealed that two of the three locally abundant zooxanthellate bioeroding species were absent from a highly turbid reef, Sampela. My fourth research chapter investigated whether this was due to light limitation by examining the photoacclimatory capabilities of the Symbiodinium photosymbionts of Cliona aff. viridis n. sp. A. PAM chlorophyll fluorometry was employed in a 25 day shading experiment and Symbiodinium of C. aff. viridis n. sp. A demonstrated an ability to photoacclimate to extreme light reduction and recover quickly when conditions returned to normal. My results demonstrate that the absence of this species at Sampela is not due to light limitation but possibly due to other stressors associated with turbidity, e.g. suspended sediment.  My final chapter was an assessment of the environmental drivers of rates of bioerosion in Spheciospongia cf. vagabunda, a common species in the Wakatobi. Erosion rates were determined from changes in dry-weight of calcareous substrates with attached grafts of S. cf. vagabunda after a year deployment across seven reef sites. The average bioerosion rate was 12.0 kg m⁻² sponge tissue yr⁻¹ (± 0.87 SE), but differed between sites and was negatively correlated with settled sediment depth. Bioerosion by this species can play a significant part in the carbonate budget on reefs where it is abundant (up to 20% of available substrate on some reefs in the Wakatobi) but is likely reduced on highly sedimented reefs.  In summary, the Wakatobi bioeroding sponge assemblage is diverse and overall, both adult abundance and recruitment are primarily driven by the availability of dead calcareous substrates. Therefore, further coral mortality and a subsequent rise in the availability of dead substrate in the region is likely to result in increased abundance of bioeroding sponges. However, not all forms of reef degradation will benefit these sponges; turbid and sedimented reefs will likely constitute stressful habitats for some bioeroding sponge species and assemblages in these environments will be comprised of fewer more resilient species.</p>

scholarly journals Sponge bioerosion and habitat degradation on Indonesian coral reefs

2021 ◽  
Author(s):  
◽  
Joseph Marlow
Keyword(s):  
Coral Reefs ◽  
Habitat Degradation ◽  
Sponge Species ◽  
Environmental Drivers ◽  
Light Limitation ◽  
Sponge Tissue ◽  
Assemblage Composition ◽  
Larval Recruitment ◽  
Reef Degradation ◽  
The Common

<p>Coral reefs are among the most diverse ecosystems on the planet, yet they are also sensitive to anthropogenic disturbances that can degrade these systems. On many degraded reefs, large increases in bioeroding sponge abundance have occurred. On healthy reefs these sponges contribute to species diversity and habitat complexity, however there is growing concern that their proliferation on degraded reefs could lead to a state of net-erosion. In the Southeast Asian Indo-Pacific, the ecology of bioeroding sponges in relation to coral degradation has been poorly studied compared to other coral reef regions. This thesis aims to increase our understanding of the ecology of these sponges in the Wakatobi region of Indonesia, and their likely trajectory if reefs continue to degrade in the region.  My first research chapter aimed to identify the common bioeroding sponge species of the Wakatobi. This was achieved through in-water surveys, and subsequent spicule and phylogenetic analysis. This resulted in the identification of eight commonly occurring Wakatobi bioeroding sponge species, two of which are described for the first time. The assemblage composition was distinctly different from the only other bioeroding sponge study in Indonesian waters (Calcinai et al. 2005), highlighting the need for more clionaid taxonomic information from the region.  Having identified the common bioeroding sponge species in the region, my second chapter assessed the major environmental drivers of the abundance and assemblage composition of these sponges. Abundance surveys were conducted at 11 reef sites characterised by different environmental conditions and states of reef health. Bioeroding sponges occupied 8.9% of suitable substrate, and differences in abundance and assemblage composition were primarily attributed to differences in the availability of dead substrate. However, abundance was lowest at a sedimented and turbid reef, despite abundant dead substrate availability. This indicates a limited resilience in some species to conditions associated with terrestrial run-off and that not all forms of reef degradation are beneficial for bioeroding sponges. The capacity to increase spatial occupation of degraded reefs is also dependent upon larval recruitment and my third chapter was a two year recruitment study using in situ experimental calcareous blocks. Recruitment occurred rapidly and consistently with bioeroding sponges recruiting to approximately 70% of experimental blocks and exhibiting a preference for settlement on uncolonised dead calcareous substrates. The importance of substrate settlement cues and extent of larval dispersal appeared to differ between species, indicative of different recruitment mechanisms. Any significant increase in the availability of exposed calcareous substrate (e.g. following a mass coral bleaching event) is therefore likely to result in widespread increases in bioeroding sponge recruitment.  Surveys conducted in my second research chapter revealed that two of the three locally abundant zooxanthellate bioeroding species were absent from a highly turbid reef, Sampela. My fourth research chapter investigated whether this was due to light limitation by examining the photoacclimatory capabilities of the Symbiodinium photosymbionts of Cliona aff. viridis n. sp. A. PAM chlorophyll fluorometry was employed in a 25 day shading experiment and Symbiodinium of C. aff. viridis n. sp. A demonstrated an ability to photoacclimate to extreme light reduction and recover quickly when conditions returned to normal. My results demonstrate that the absence of this species at Sampela is not due to light limitation but possibly due to other stressors associated with turbidity, e.g. suspended sediment.  My final chapter was an assessment of the environmental drivers of rates of bioerosion in Spheciospongia cf. vagabunda, a common species in the Wakatobi. Erosion rates were determined from changes in dry-weight of calcareous substrates with attached grafts of S. cf. vagabunda after a year deployment across seven reef sites. The average bioerosion rate was 12.0 kg m⁻² sponge tissue yr⁻¹ (± 0.87 SE), but differed between sites and was negatively correlated with settled sediment depth. Bioerosion by this species can play a significant part in the carbonate budget on reefs where it is abundant (up to 20% of available substrate on some reefs in the Wakatobi) but is likely reduced on highly sedimented reefs.  In summary, the Wakatobi bioeroding sponge assemblage is diverse and overall, both adult abundance and recruitment are primarily driven by the availability of dead calcareous substrates. Therefore, further coral mortality and a subsequent rise in the availability of dead substrate in the region is likely to result in increased abundance of bioeroding sponges. However, not all forms of reef degradation will benefit these sponges; turbid and sedimented reefs will likely constitute stressful habitats for some bioeroding sponge species and assemblages in these environments will be comprised of fewer more resilient species.</p>

scholarly journals Nitrogen enrichment in macroalgae following mass coral mortality

Coral Reefs ◽  
2021 ◽  
Author(s):  
Eleanor J. Vaughan ◽  
Shaun K. Wilson ◽  
Samantha J. Howlett ◽  
Valeriano Parravicini ◽  
Gareth J. Williams ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Coral Cover ◽  
Strong Association ◽  
French Polynesia ◽  
Mass Mortality ◽  
Transplant Experiment ◽  
Bleaching Event ◽  
Coral Mortality ◽  
Absolute Increase ◽  
Inorganic Matter

AbstractScleractinian corals are engineers on coral reefs that provide both structural complexity as habitat and sustenance for other reef-associated organisms via the release of organic and inorganic matter. However, coral reefs are facing multiple pressures from climate change and other stressors, which can result in mass coral bleaching and mortality events. Mass mortality of corals results in enhanced release of organic matter, which can cause significant alterations to reef biochemical and recycling processes. There is little known about how long these nutrients are retained within the system, for instance, within the tissues of other benthic organisms. We investigated changes in nitrogen isotopic signatures (δ15N) of macroalgal tissues (a) ~ 1 year after a bleaching event in the Seychelles and (b) ~ 3 months after the peak of a bleaching event in Mo’orea, French Polynesia. In the Seychelles, there was a strong association between absolute loss in both total coral cover and branching coral cover and absolute increase in macroalgal δ15N between 2014 and 2017 (adjusted r2 = 0.79, p = 0.004 and adjusted r2 = 0.86, p = 0.002, respectively). In Mo’orea, a short-term transplant experiment found a significant increase in δ15N in Sargassum mangarevense after specimens were deployed on a reef with high coral mortality for ~ 3 weeks (p < 0.05). We suggest that coral-derived nutrients can be retained within reef nutrient cycles, and that this can affect other reef-associated organisms over both short- and long-term periods, especially opportunistic species such as macroalgae. These species could therefore proliferate on reefs that have experienced mass mortality events, because they have been provided with both space and nutrient subsidies by the death and decay of corals.

scholarly journals On the geophysical processes impacting palaeo-sea-level observations

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yusuke Yokoyama ◽  
Anthony Purcell
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Global Climate ◽  
Sea Level Change ◽  
Sea Level Changes ◽  
Factors Affecting ◽  
Ice Volume ◽  
Level Change ◽  
Recent Developments ◽  
Geophysical Processes

AbstractPast sea-level change represents the large-scale state of global climate, reflecting the waxing and waning of global ice sheets and the corresponding effect on ocean volume. Recent developments in sampling and analytical methods enable us to more precisely reconstruct past sea-level changes using geological indicators dated by radiometric methods. However, ice-volume changes alone cannot wholly account for these observations of local, relative sea-level change because of various geophysical factors including glacio-hydro-isostatic adjustments (GIA). The mechanisms behind GIA cannot be ignored when reconstructing global ice volume, yet they remain poorly understood within the general sea-level community. In this paper, various geophysical factors affecting sea-level observations are discussed and the details and impacts of these processes on estimates of past ice volumes are introduced.

scholarly journals Stokes drift through corals

2021 ◽  
Author(s):  
Joseph J. Webber ◽  
Herbert E. Huppert
Keyword(s):  
Coral Reef ◽  
Coral Reefs ◽  
Porous Layer ◽  
Large Scale ◽  
Fluid Layer ◽  
Ocean Waves ◽  
Stokes Drift ◽  
Inviscid Fluid ◽  
Porous Bed ◽  
Vertical Drift

AbstractMotivated by shallow ocean waves propagating over coral reefs, we investigate the drift velocities due to surface wave motion in an effectively inviscid fluid that overlies a saturated porous bed of finite depth. Previous work in this area either neglects the large-scale flow between layers (Phillips in Flow and reactions in permeable rocks, Cambridge University Press, Cambridge, 1991) or only considers the drift above the porous layer (Monismith in Ann Rev Fluid Mech 39:37–55, 2007). Overcoming these limitations, we propose a model where flow is described by a velocity potential above the porous layer and by Darcy’s law in the porous bed, with derived matching conditions at the interface between the two layers. Both a horizontal and a novel vertical drift effect arise from the damping of the porous bed, which requires the use of a complex wavenumber k. This is in contrast to the purely horizontal second-order drift first derived by Stokes (Trans Camb Philos Soc 8:441–455, 1847) when working with solely a pure fluid layer. Our work provides a physical model for coral reefs in shallow seas, where fluid drift both above and within the reef is vitally important for maintaining a healthy reef ecosystem (Koehl et al. In: Proceedings of the 8th International Coral Reef Symposium, vol 2, pp 1087–1092, 1997; Monismith in Ann Rev Fluid Mech 39:37–55, 2007). We compare our model with field measurements by Koehl and Hadfield (J Mar Syst 49:75–88, 2004) and also explain the vertical drift effects as documented by Koehl et al. (Mar Ecol Prog Ser 335:1–18, 2007), who measured the exchange between a coral reef layer and the (relatively shallow) sea above.

scholarly journals Progress in Research on Carbon Nanotubes Reinforced Cementitious Composites

2015 ◽  
Vol 2015 ◽  
pp. 1-16 ◽  
Author(s):  
Qinghua Li ◽  
Jintao Liu ◽  
Shilang Xu
Keyword(s):  
Carbon Nanotubes ◽  
Large Scale ◽  
High Strength ◽  
Cementitious Composites ◽  
Scale Production ◽  
Multiwalled Carbon ◽  
Factors Affecting ◽  
Environment And Health ◽  
Research Activities ◽  
Major Factors

As one-dimensional (1D) nanofiber, carbon nanotubes (CNTs) have been widely used to improve the performance of nanocomposites due to their high strength, small dimensions, and remarkable physical properties. Progress in the field of CNTs presents a potential opportunity to enhance cementitious composites at the nanoscale. In this review, current research activities and key advances on multiwalled carbon nanotubes (MWCNTs) reinforced cementitious composites are summarized, including the effect of MWCNTs on modulus of elasticity, porosity, fracture, and mechanical and microstructure properties of cement-based composites. The issues about the improvement mechanisms, MWCNTs dispersion methods, and the major factors affecting the mechanical properties of composites are discussed. In addition, large-scale production methods of MWCNTs and the effects of CNTs on environment and health are also summarized.

Species Responses to Grazing and Environmental-Factors in an Arid Halophytic Shrubland Community

1987 ◽  
Vol 35 (2) ◽  
pp. 135 ◽  
Author(s):  
RB Hacker
Keyword(s):  
Environmental Factors ◽  
Soil Salinity ◽  
Large Scale ◽  
Chemical Properties ◽  
Grazing Pressure ◽  
Aerial Photographs ◽  
Small Scale ◽  
Factors Affecting ◽  
Species Responses

Species responses to grazing and environmental factors were studied in an arid halophytic shrubland community in Western Australia. The grazing responses of major shrub species were defined by using reciprocal averaging ordination of botanical data, interpreted in conjunction with a similar ordination of soil chemical properties and measures of soil erosion derived from large-scale aerial photographs. An apparent small-scale interaction between grazing and soil salinity was also defined. Long-term grazing pressure is apparently reduced on localised areas of high salinity. Environmental factors affecting species distribution are complex and appear to include soil salinity, soil cationic balance, geomorphological variation and the influence of cryptogamic crusts on seedling establishment.

Factors affecting post-fire seedling establishment of selected mallee understorey species

2000 ◽  
Vol 48 (1) ◽  
pp. 59 ◽  
Author(s):  
J. S. Cohn ◽  
R. A. Bradstock
Keyword(s):  
Large Scale ◽  
Prescribed Burning ◽  
New South ◽  
Eucalyptus Species ◽  
Factors Affecting ◽  
Acacia Species ◽  
Introduced Herbivores ◽  
South Wales ◽  
Rabbit Grazing ◽  
Seedling Germination

Factors affecting the survival of post-fire germinants in mallee communities, in central western New South Wales, were examined. Experiments compared the relative effects of native and introduced herbivores (kangaroos, goats, rabbits), after small- and large-scale fires (20–50 and > 10 000 ha, respectively), with particular emphasis on edge effects, seedling clustering, topography and eucalypt canopy presence. The experiments (1985–1997) focused on common understorey species Acacia rigens Cunn. ex Don, A. wilhelmiana F.Muell. and Triodia scariosa N.T.Burb. subsp. scariosa, in mallee dominated by Eucalyptus species. Following a large fire (1985), high spring rainfall and rabbit grazing on A. rigens only, survival of Acacia species and T. scariosa remained relatively high 4 years later (60–70%). After small burns (1987, 1988), low spring rainfall and grazing by rabbits and kangaroos, survival of Acacia species declined to between 0 and 30% of the germinants by the second summer. In most cases, local extinction had occurred within 8 years. After small burns (1988, 1989) and low spring rainfall, the survival of T. scariosa declined to between 0 and 35% of germinants by the second summer (effect of grazing unknown). No consistent effect of edge, topography and eucalypt canopy was found. Survival of clustered Acacia seedlings was between 10 and 20% lower than unclustered seedlings. Given the high frequency of low rainfall and its interaction with grazing, prescribed burning of mallee for wildfire control and nature conservation may require the local elimination of rabbits and a reduction in kangaroo numbers, especially in the first spring and summer following seedling germination.

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