Reef Size Research Articles

Location and reef size drive oyster reef restoration success

Optimizing habitat restoration success requires understanding how restoration location and design enhance the persistence and function of a restored habitat. Particular attention to the configuration of structure and its interaction with landscape‐scale processes is critical for enhancing the habitat value of restored areas. We monitored six subtidal restored oyster reefs in Pamlico Sound, North Carolina, United States, to identify how oyster demographics responded to initial habitat characteristics (e.g. reef area, volume, vertical relief, and perimeter‐to‐area ratio) and how changes in habitat characteristics over time altered suitability for oysters. Changes in reef habitat were measured by repeated mapping using bathymetric and side‐scanning sonar systems. A 2‐year time series of oyster demographic data quantified oyster response to habitat changes over time. All reefs provided habitat for the settlement and growth of oysters. Within 2 years of restoration, relative differences in oyster recruitment and survival emerged and were related to variations in reef location and two‐dimensional habitat characteristics among reefs, namely reef area and perimeter‐to‐area ratio. Larger reefs that were less fragmented resisted burial from sedimentation and enhanced oyster densities and biomass relative to smaller, more fragmented reefs that became heavily sedimented and failed to support oyster recruitment and survival. Positive feedback mechanisms between habitat characteristics and oyster recruitment success were established within 1 year of restoration and were likely driven by landscape‐scale processes such as sediment dynamics and larval supply. To improve restoration success, we recommend creating larger reef surfaces with low perimeter‐to‐area ratios in areas that promote habitat persistence.

High-resolution imagery of the coral reefs of Gorgona Island, Colombian Pacific Ocean: An improved view for monitoring and research

The shape and size of a coral reef are both key factors influencing its ecology and biodiversity. These parameters play a fundamental role in the creation of specific habitats that support a rich biodiversity. They also greatly influence its resilience to climatic events and external influences. Here we present a practical example of photogrammetric reconstruction of the best developed coral reefs of the Colombian Pacific, located at Gorgona Island. Using unoccupied aerial vehicles (drones) and Geographic Information Systems (GIS), we produced high resolution orthophotomosaics and precise contour maps of four reefs and updated estimates of reef areas. We illustrate the improved accuracy of these maps in comparison with maps obtained from satellite imagery and conclude by highlighting the usefulness of drones to locate, measure, and monitor small coral reefs.

Seascape configuration influences big blue octopus (Octopus cyanea) catches: Implications for a sustainable fishery

Seascape configuration is known to influence fish distribution and abundance in coastal waters. However, there is little information regarding how the shape of the coastal seascape influences catches of landed fisheries species, particularly so in the understudied western Indian Ocean (WIO). With focus on big blue octopus (Octopus cyanea), which is a widely found cephalopod species in the WIO, we compared landed catches (biomass, catch rate, and density) in submerged and exposed reefs, and explored the influence of proximity to fishing villages and reef habitat size on octopus landings. We used fishery-dependent data collected between 2018 and 2020 from eight landing sites spread across the Tanzanian coast. We found a strong relationship between biomass of octopus catch and distance from fished reefs to fishing villages, with higher fished biomass on reefs farther away. Octopus densities were higher, while catch rates were lower, on reefs very close to (within one km distance from) fishing villages compared to more distant reefs. In general, submerged reefs provided higher catches than exposed reefs. The low octopus catches on the exposed reefs were attributed to high fishing pressure, while submerged reefs that are only accessible through diving provide optimal areas for octopuses to grow. Octopus catches were, however, not significantly affected by reef size. The findings suggest that management policies should proportionate fishing efforts to ensure sustainable exploitation of reefs and associated fishery resources.

Increases in reef size, habitat and metacommunity complexity associated with Cambrian radiation oxygenation pulses

Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation has not been quantified, nor have the causal evolutionary processes been constrained. Here we present ecological analyses of Cambrian archaeocyath sponge reef communities on the Siberian Platform (525–514 Ma). During the oxic pulse at ~521–519 Ma, we quantify reef habitat expansion coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519–516.5 Ma). A later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide environmental responses. These metrics confirm that oxygenation events created temporary pulses of evolutionary diversification and enhanced ecosystem complexity, potentially via the expansion of habitable space, and increased archaeocyath individual and reef longevity in turn leading to niche differentiation. Most notably, we show that progression towards increasing biodiversity and ecosystem complexity was episodic and discontinuous, rather than linear, during the Cambrian Radiation.

Lagoon infilling by coral reef sand aprons as a proxy for carbonate sediment productivity

AbstractSand aprons are distinctive landforms that offer important insights into sedimentary dynamics for reef platform development. Here we link temporal and spatial scales of 21 sand aprons in the southern Great Barrier Reef to understand their Holocene formation and evolution in response to relative sea-level changes, the depth of the Pleistocene base, and contemporary morphodynamics. Our results show that lagoon infilling is a function of reef size and is a self-limiting process controlled by hydrodynamics and relative sea-level changes. Lagoon infilling does not depend on the type of reef or degree of exposure to waves, but it could reflect past wave climates. Our carbonate productivity estimates based on lagoon infilling are remarkably similar to those inferred from habitat classification. Finally, we hypothesize that current carbonate productivity has slowed because of the effects of climate change.

Study on flow field characteristics of box artificial reef

Based on Zhuhai Miaowan artificial reef demonstration project, this paper studied the flow field characteristics of single box artificial reef and reef group under different spacing by using computational fluid dynamics (CFD) method. The results show that the box artificial reef has a significant effect on flow field. The maximum upwelling height near the reef is about 1.4 times the reef height, and the length of the back vortex is twice the reef size. In the reef group arrangement, the flow field distribution plays the best performance at the 5m spacing arrangement. The research results can provide guidance for reef structure optimization and practical arrangement in site.

Spatial Dynamics of Two Host-Parasite Relationships on Intertidal Oyster Reefs

Intertidal reefs comprised of the eastern oyster (Crassostrea virginica) have long experienced habitat loss, altering habitat patch characteristics of size and distance from edge to interior, potentially influencing spatial dynamics of host-parasite relationships. Using two parasitic relationships, one between eastern oyster host and parasitic oyster pea crab (Zaops ostreum) and the other between a xanthid crab (Eurypanopeus depressus) and a parasitic rhizocephalan barnacle (Loxothylacus panopaei), we examined how host-parasite population characteristics varied on intertidal reefs by season, reef size, and distance from edge to interior. Pea crab prevalence was more related to habitat characteristics rather than host density, as pea crab prevalence was the highest on large reefs and along edges, areas of comparatively lower oyster densities. Reef size did not influence densities of parasitized or non-parasitized xanthid crabs, but densities varied from edge to interior. Non-parasitized xanthids had significantly lower densities along the reef edge compared to more interior reef locations, while parasitized xanthid crabs had no significant edge to interior pattern. Organismal size had a varied relationship based upon habitat characteristics, as pea crab carapace width (CW) varied interactively with season and reef size, whereas CW of parasitized/non-parasitized xanthid crabs varied significantly between edge and interior locations. These results demonstrated that influential habitat characteristics, such as patch size and edge versus interior, are both highly species and host-parasite specific. Therefore, continued habitat alteration and fragmentation of critical marine habitats may further impact spatial dynamics of host-parasite relationships.

Recruitment enhancement varies by taxonomic group and oyster reef habitat characteristics.

The rapid loss of coastal and estuarine biogenic habitats has reduced the delivery of valuable ecosystem services, resulting in calls for increased habitat restoration. Yet, a lack of information on how key habitat characteristics (e.g., area, vertical relief, age) influence the ability of restored habitats to deliver these ecosystem services hinders efforts to maximize the return on restoration investments. We conducted a meta-analysis to assess the influence of reef type (natural or restored), taxa, and restored reef size, vertical relief, age, and tidal zone on the presence and magnitude of recruitment enhancement for nekton (i.e., fish and swimming crabs). Both intertidal and subtidal reefs, as well as restored and natural reefs, enhanced nekton recruitment, though there was variation among taxonomic groups with reef types. Recruitment enhancement was more common across taxa on restored (six families) than on natural (one family) reefs. Resident nekton families were more consistently enhanced than transient families. Nekton enhancement varied with a number of restored reef characteristics. Recruitment enhancement increased with greater reef size across taxa, decreased with higher vertical relief for two families, showed maximum recruitment around a single intertidal reef age for one family, and showed minimum recruitment around a single subtidal reef age for three families. Understanding variation across species in response to key design elements will improve restoration success and enhance return on investment. Moving forward, we recommend studies that vary reef habitat characteristics independently and in combination to identify how variation in these characteristics interact to influence nekton recruitment enhancement by oyster reefs.

Can we enhance ecosystem-based coastal defense by connecting oysters to marsh edges? Analyzing the limits of oyster reef establishment

Nature-based coastal defense schemes commonly value bivalve reefs for i) reducing coastal erosion in the intertidal and for ii) forming fringing reefs near salt marsh edges to protect them against lateral retreat. The capacity for a reef to reduce erosion increases at a higher position in the tidal frame as the lower over-lying water level magnifies the influence of the reef on wave attenuation. Unfortunately, ecological constraints on reef development typically limit their practical application in coastal protection schemes to the lower intertidal, as bivalves grow best with long inundation times. In micro-tidal areas this is a lesser problem, given the close proximity of lower and upper intertidal ecosystems in space. By contrast, in meso- and macro-tidal estuaries, bivalve reefs tend to form hundreds of meters away from existing marshes, nullifying any wave-protective benefits. In this study, we produce evidence that with the assistance of management measures, widespread reef formation is possible on open mudflats, including bordering the marsh edge in meso- and macro-tidal estuaries, where natural reef formation is normally strongly limited.In four locations throughout the meso- to macro-tidal Dutch Scheldt estuary, we observed the presence of individuals of two major intertidal reef-forming bivalves, Pacific oysters (Crassostrea gigas) and blue mussels (Mytilus edulis), within low-lying Spartina anglica-dominated marshes. As these communities lie well outside of the expected range of reef formation, this observation suggests the existence of mechanisms that extend the habitable range of these bivalves. In a series of field experiments, we first demonstrate how the stabilization of shell-substrate within the marsh promotes successful establishment and adult survival. Secondly, by placing artificial stable substrate in transects from the subtidal up to the marsh edge, we demonstrate that bivalve establishment is possible throughout a much larger range of the intertidal than where natural reefs occur. The effectiveness of stable substrate in stimulating bivalve establishment is likely a consequence of bridging size-dependent thresholds that limit the effective range for natural reef formation on tidal flats. The success of this approach is tempered by a consistent decrease in reef size and growth at higher elevations, suggesting that the optimal reef position for utility in coastal defense lies at an intermediate tidal position, well above the observed range of natural occurrence, but below the maximum achievable upper limit of reef formation. Together this work provides a pathway forward concerning how artificial reefs may be fostered to increase their utility as a nature-based flood defense measure.

Assessing mechanical response of CO2 storage into a depleted carbonate reef using a site-scale geomechanical model calibrated with field tests and InSAR monitoring data

Geomechanical risks of injection have raised concerns regarding secure CO2 storage. In this work, a combined monitoring and modeling approach is used to assess the stress changes and surface uplift associated with CO2 injection into a depleted carbonate reef of the Michigan basin. A site-scale geomechanical model is built by assigning mechanical properties of formations using well-log and experimental data. Gravity load is applied to the model to estimate the vertical component of stress as well as different lateral boundary displacement scenarios to estimate horizontal stresses. We used a poroelastic pressure-dependent model (instead of a linear elastic mechanical earth model) to calibrate initial stresses using hydraulic fracture test data measured at depleted reservoir status. Multi-phase fluid flow-geomechanical simulations are performed to estimate the poroelastic response during (1) primary depletion (2) field-scale CO2 injection phase (3) a hypothetical forecast scenario in which well bottom hole pressure (BHP) reach 45000 KPa. The predicted surface uplift is less than 1 mm at the end of the field-scale CO2 injection phase which is in good agreement with Interferometric Synthetic Aperture Radar (InSAR) uplift measurement. Although the InSAR data shows an insignificant uplift, hydromechanical modeling of injection shows that CO2 injection still causes reservoir deformation emphasizing the role of carbonate overburden and reservoir formation mechanical properties and limited size of reef on diminishing the surface deformation. Modeling indicates poroelastic response of caprock matters to estimate uplift. The lower permeability of the top two layers provides additional barrier to large uplift. Also, history of subsidence due to production should be accounted to predict uplift due to a follow up injection correctly. This study shows the significance of combining a calibrated geomechanical model with field measured stresses and monitoring data to be used as a tool to ensure the safety of CO2 storage.

Kelp patch size and density influence secondary productivity and diversity of epifauna

Habitat‐forming ecosystem engineers are the foundation of many marine ecosystems where they support diverse and productive food‐webs. A reduction in their patch size or density may affect the productivity, biodiversity and stability of these ecosystems. We determined the effects of different densities and patch sizes of Ecklonia radiata (the dominant kelp in southern Australia) on the secondary productivity, species richness, diversity and community structure of understory epifaunal invertebrates and how associated environmental covariates modified by kelp affected those patterns. We assessed sub‐canopy epifauna across 28 artificial reefs with transplanted E. radiata consisting of seven different patch sizes (0.12–7.68 m2) crossed with four kelp densities (0–16 kelp m−2) over two years. Epifaunal secondary productivity associated with both natural algal and standardised rope fibre habitats decreased with patch size and was elevated when kelp was absent, however, it was also high in natural habitat when there was a high density of kelp. Epifaunal productivity was positively associated with sub‐canopy light and water flow but negatively associated with the biomass of the dominant understory alga, Ulva sp. Epifaunal diversity declined with a reduction in reef size as did richness which correlated with a loss of algal species richness. Community structure of epifauna also differed between small and large reefs, between reefs with and without kelp, between rope habitats at the centre and at the edge of reefs, and within natural habitat between reefs supporting high and low densities of kelp. Overall, these results indicate complex effects of E. radiata decline on epifaunal communities, with high secondary productivity associated with dense kelp stands, but also areas without kelp that are dominated by turf algae. While the loss of standing kelp from rocky reefs may result in declines in epifaunal biodiversity, where turf algae replaces kelp, the reefs may still support high secondary productivity.

An Islandscape IFD: Using the Ideal Free Distribution to Predict Pre-Columbian Settlements from Grenada to St. Vincent, Eastern Caribbean

ABSTRACT This study employs an ideal free distribution (IFD) model to conduct a fine-grained analysis of environmental factors affecting the pre-Columbian colonisation sequence and settlement patterning in the southern Lesser Antilles of the Eastern Caribbean. We compiled a database of all known archaeological site locations and associated chronological data from St. Vincent, the Grenadines, and Grenada, and vetted this dataset for accuracy. We then performed multivariate statistical analysis of the vetted site data and 24 environmental variables hypothesised to influence settlement habitat quality, including soil attributes, proximity to freshwater/stream beds, structure and sizes of marine environments, and net primary productivity (NPP) layers. Iterative testing and refinement of the model allowed for the creation of a predictive map of pre-Columbian archaeological sites over time. Results indicate proximity to freshwater wetlands, NPP, and reef size were important variables influencing habitat choice. Additionally, latitude (distance from the equator) was also a significant variable, indicating support for a proposed colonisation of the southern Lesser Antilles that began in the northern Caribbean, rather than the south. Lastly, we provide a site inventory and map of predicted site locations that can aid in the management of threatened archaeological resources within the study region.

Zonation and reef size significantly influence fish population structure in an established marine protected area, iSimangaliso Wetland Park, South Africa

To demonstrate conservation effects resulting from marine protected areas, many studies rely on spatial comparisons between areas afforded different levels of protection. These spatial comparisons can be confounded if the habitat and reef size are dissimilar and not accounted for in the statistical analysis. Taking into account reef size (obtained from multibeam sonar data) and benthic habitat structure, this research tested the effect of management zonation (No-take Sanctuary Zone = NTSZ; Controlled Pelagic Zone = CPZ) on the population structure (relative abundance and average biomass) of six fish species in the iSimangaliso Wetland Park, South Africa. Furthermore, this study tested the effect of ignoring reef size in spatial comparisons. Our results showed that reef size had a significant positive effect on the relative abundance and average biomass of most, but not all species. When reef size was included in the models, the results showed that two of the six species presented no effect of management zone; two appeared to be directly affected by the permitted (past and present) fishing activity in the CPZ; and the last two species appeared to be affected by the disturbance caused by the diving and/or boating activity in the CPZ. Excluding reef size from the analysis consistently resulted in the predicted relative abundance and average biomass decreasing in the CPZ and increasing in the NTSZ. This effect was most marked in the average biomass data, as the management zone effect changed from negligible to significant for five of the six species. Our results highlight the importance of accounting for the reef size, or area of suitable habitat, when conducting spatial comparisons among species and illustrate the potential impact of the trade-off required to accommodate human needs within protected spaces.

How Can You Be Happy?

How Can You Be Happy? Steve Almond (bio) The Dugans met at the Inspiration Academy, the school for at-risk kids where Craig volunteered. He was leading a tour for potential donors. The Academy was in a part of the city Ellie had never visited so she wound up ten minutes late, a little tipsy on her heels, with a lopsided smile and a sweet honking laugh. Craig desired her almost at once. She concurred. Craig was handsome and charming. When he nodded at the uniformed students who called out to him—Hey, Mister D! Mister Deeeee!—Ellie found herself a little out of breath. Soon they were eating rich foods and drinking wine and making love with a fierce and procreative abandon. Why the hell not? Craig was forty, Ellie was thirty and change. Then Craig was on his knees in front of the school cafeteria where they first met, clutching a ring that had belonged to his Dutch grandmother. Ellie nodded and wept while a small chorale of at-risk kids, faces pressed to the windows, cheered wildly. It was like a fairytale, the happy part at the end where everything speeds up, and a few days later, or months—who knows? who cares?—they were getting hitched at her parents’ estate on the Cape, with a raw bar the size of the Great Barrier Reef and a lawn so vast and luminous it outlined the earth’s curvature. Ellie wore an off-white dress; this was her second wedding in five years, though nobody said anything about this or about anything that might intrude upon the sense of boundless good fortune that their union seemed to portend. ________ They had the babies, two in three years. The process left them bleary with gratitude, handing the little loaves back and forth in the cozy flat where Craig had lived for many years as a bachelor. Then Ellie wanted a house. Actually, she’d always wanted a house. The best her first husband could do was a condo in Vail. But Craig had inherited real estate from his father. They argued, just a little at first. Ellie was a bulldog or maybe something closer to a Doberman. She felt their happiness depended on having space and family support, and wasn’t buying a home an investment? Wasn’t that the whole lesson of the Dugan legacy—that the market always goes up? When he finally relented, she straddled him and screwed him silly then scrolled through all the Zillow listings she’d saved. This went on for a month: real estate sex, the terminal stage of courtship. They settled on a colonial in the town where her parents lived, a house [End Page 124] Craig did not actually want to purchase, though he convinced himself it would make his wife happy and therefore him. They began to host cocktail parties and visited her folks, who had a pool the kids loved. This was in addition to Augusts on the Cape and holidays and little unannounced drop-ins from Grandma Beatrice, always with a gift in hand for the littles and sunny ideas about vacation destinations and interior design elements. Craig began to suspect that Ellie didn’t want to forge a family of her own. She wanted to be reabsorbed into the family of her youth, the summer afternoons marked by the idle industry of the rich: tennis, golf, the beach, the shops, the antic blur of cocktail hour. Her father Hank was a marketing executive straight out of Cheever, a good-natured alcoholic who had had the temerity, a decade earlier, to sober up and leave Bea for seven harrowing months before returning, chastened, to bride and bottle. Every time they shook hands, Hank grasped his forearm, like a diver uncertain he would reach the surface in time. Ellie starved off her baby weight and cross-trained. She had been a promising gymnast as a young girl until a gruesome dismount at age nine. The fall had shattered her orbital bone and caused nerve damage in her cheek. It had taken her months to recuperate, a steel plate, three cranial surgeries. She told Craig...

Microfacies, depositional environments and meter-scale cycles of the middle jurassic Tuwaiq Mountain formation, central Saudi Arabia

The Jurassic succession in Saudi Arabia represents the most prolific succession in the world. However, a detailed microfacies and paleoenvironmental model description, high-frequency cycles (HFC) analysis, and paleoenvironmental reconstruction of the main source rock interval for the Jurassic reservoirs, the Callovian Tuwaiq Mountain Formation (TMF) are poorly documented. This article reports on a study of the TMF, and discusses the succession of the microfacies, paleoenvironments, HFC, and depositional sequences, and paleoenvironmental constrains. On the basis of detailed field and lab work, 8 microfacies were recognized and interpreted to be deposited in four facies belts representing the inner part of a rimmed carbonate platform including: deep lagoon, shallow lagoon, shoal and peritidal and tidal flat. Within the deep and shallow lagoonal settings, massive platy and domal coral colonies form patch reefs. These patch reefs increase in size from deep to shallow lagoon settings under response to changing in environmental conditions; grater water clarity and harder substrate promoted larger patch reef size in shallow lagoon. Patch reefs decrease in size and disappear in shoal settings. The siliciclastic input was minute and could have been derived from tidal channels and/or windblown dust from the Arabian Shield. The stacking pattern of the microfacies revealed that the TMF represents a regressive cycle (3rd order depositional sequence), which is formed by repeated aggrading to prograding medium and small scale cycles. The HFC analysis gave an estimated duration of a small cycle about 45 Kyr, and an average rate of carbonate accumulation of 0.0455 m/Kyr. Therefore, medium and small scale cycles possibly represent 4th and 5th order depositional cycles, respectively, which are orbitally driven by high frequency eustatic fluctuations (Milankovitch cycles “obliquity”). The paleoenvironmental reconstruction revealed that the deposition occurred under the influence of occasional storm events with normal marine euhaline salinity and becomes more restricted towards the proximal part (lagoon to tidal flat).

The effects of intertidal oyster reef habitat characteristics on faunal utilization

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 581:57-70 (2017) - DOI: https://doi.org/10.3354/meps12261 The effects of intertidal oyster reef habitat characteristics on faunal utilization Marc H. Hanke1,2,*, Martin H. Posey1, Troy D. Alphin1 1Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403, USA 2Present address: Honors College, University of Houston, 212 MD Anderson Library, 4333 University Dr., Houston, TX 77204-2001, USA *Corresponding author: marc.h.hanke@gmail.com ABSTRACT: The presence, abundance, and distribution of organisms within a landscape are highly dependent on the composition, quality, and configuration of habitat patches. Intertidal oyster Crassostrea virginica reefs provide a structured habitat for many organisms; however, declining oyster populations have induced reef fragmentation and loss. Over 2 years (2011-2012), we evaluated naturally occurring fringing and patch intertidal oyster reefs in southeastern North Carolina, USA, to determine how varied reef type, size, and distance from edge to interior influenced the associated benthic macrofauna and mobile nekton. In addition, the effects of size and edge vs. interior were examined on constructed intertidal reefs at 2 different locations. On the natural reefs, species richness of benthic macrofauna and mobile nekton were significantly increased on fringing reefs. Benthic macrofauna richness significantly decreased on large natural reefs, whereas mobile nekton richness significantly increased off of large reefs. Further, associated benthic macrofauna richness significantly decreased along the reef edge, whereas mobile nekton diversity increased along the reef/open bottom interface. Species richness and densities for benthic macrofauna increased with created reef size, while there was greater species richness and diversity and dissimilar communities for mobile nekton along constructed reef edges. Habitat specificity may influence utilization for mobile nekton, as resident organisms with limited vagility had a stronger response to habitat characteristics. Thus, utilization of intertidal oyster reefs can be highly structured by habitat characteristics on many scales, and should be considered when examining species interactions, ecosystem management, and future restoration efforts. KEY WORDS: Habitat characteristics · Habitat heterogeneity · Patch size · Edge effects · Mobile nekton · Benthic macrofauna · Habitat fragmentation · Habitat restoration · Oyster reefs · Crassostrea virginica Full text in pdf format PreviousNextCite this article as: Hanke MH, Posey MH, Alphin TD (2017) The effects of intertidal oyster reef habitat characteristics on faunal utilization. Mar Ecol Prog Ser 581:57-70. https://doi.org/10.3354/meps12261 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 581. Online publication date: October 13, 2017 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2017 Inter-Research.

Coral Reef Development as an Indicator of Seal Level Fluctuation: A Preliminary Study on Pleistocene Reef in Bulukumba, South Sulawesi

DOI:10.17014/ijog.3.1.53-66Pleistocene reefs in eastern part of Indonesia are abundantly found along the coast as raised reef. They express highly tectonized and/or uplifted area characterized by several terraces. Therefore the reef size is narrow. This research is located at Bira District of Bulukumba Regency or it lies at the southern tip of South Sulawesi Peninsula. The objective of this research is to define depositional environment based on coral development. Several methods were applied such as intersect lines which were perpendicular to the cliff, geochemical and petrographic analyses, as well as paleoenvironment interpretation. Three facies are described at the Pleistocene reef, namely 1) Reef Front Facies, 2) Reef Core Facies, 3) Back Reef Facies. Based on facies association and organism accumulation, the depositional environment of Pleistocene reef is interpreted to be developed in a small reef complex on an unstable basement. The reef has experienced at least 3 (three) times of sea level fluctuation.

Zooplanktivory is a key process for fish production on a coastal artificial reef

Artificial reefs continue to be deployed in coastal areas to enhance local fisheries. An important factor influencing the success of artificial reefs may be the provision of refuge for zooplank- tivorous fishes, which use artificial reefs as a base to forage the surrounding zooplankton. A numerical model was developed to quantify this trophic pathway on a designed coastal artificial reef, using field-parameterised data for zooplankton biomass, current velocity, and the consumption rate and abundance of a reef-resident zooplanktivorous fish (Atypichthys strigatus). The model estimated that this species consumed ~2.9 kg (1.0 g m −3 ) of zoo- plankton per day on this artificial reef, which repre- sents only 0.35% of the total zooplankton biomass. The ability of this artificial reef to support ~130 kg standing stock of this species suggests that the zoo- plankton pathway is a reliable mechanism for fish production. A second model explored the influence of reef size on zooplanktivorous fish densities and the supply of zooplankton required to sustain their consumption rate. As reef size increased, the ratio between the foraging volume and refuge volume declined, meaning that small reefs have lots of food and not much refuge, and large reefs can have lots of refuge but not enough food. This indicates that reef size can be manipulated to maximise fish abun- dance while avoiding food limitation. Reef size, shape, and orientation should be considered care- fully during the planning of artificial reefs, as it can greatly influence the foraging of reef-resident zoo- planktivorous fishes and thus influence the entire reef assemblage.

Sea surface temperature as a tracer to estimate cross‐shelf turbulent diffusivity and flushing time in the Great Barrier Reef lagoon

AbstractAccurate parameterization of spatially variable diffusivity in complex shelf regions such as the Great Barrier Reef (GBR) lagoon is an unresolved issue for hydrodynamic models. This leads to large uncertainties to the flushing time derived from them and to the evaluation of ecosystem resilience to terrestrially derived pollution. In fact, numerical hydrodynamic models and analytical cross‐shore diffusion models have predicted very different flushing times for the GBR lagoon. Nevertheless, scarcity of in situ measurements used previously in the latter method prevents derivation of detailed diffusivity profiles. Here detailed cross‐shore profiles of diffusivity were calculated explicitly in a closed form for the first time from the steady state transects of sea surface temperature for different sections of the GBR lagoon. We find that diffusivity remains relatively constant within the inner lagoon (<∼20 km) where tidal current is weak, and increases linearly with sufficiently large tidal amplitude in reef‐devoid regions, but increases dramatically where the reef matrixes start and fluctuates with reef size and density. The cross‐shelf profile of steady state salinity calculated using the derived diffusivity values agrees well with field measurements. The calculated diffusivity values are also consistent with values derived from satellite‐tracked drifters. Flushing time by offshore diffusion is of the order of 1 month, suggesting the important role of turbulent diffusion in flushing the lagoon, especially in reef‐distributed regions. The results imply that previous very large residence times predicted by numerical hydrodynamic models may result from underestimation of diffusivity. Our findings can guide parameterization of diffusivity in hydrodynamic modeling.

Strong but opposingβ-diversity–stability relationships in coral reef fish communities

The 'diversity-stability hypothesis', in which higher species diversity within biological communities buffers the risk of ecological collapse, is now generally accepted. However, empirical evidence for a relationship between β-diversity (spatial turnover in community structure) and temporal stability in community structure remains equivocal, despite important implications for theoretical ecology and conservation biology. Here, we report strong β-diversity-stability relationships across a broad sample of fish taxa on Australia's Great Barrier Reef. These relationships were robust to random sampling error and spatial and environmental factors, such as latitude, reef size and isolation. While β-diversity was positively associated with temporal stability at the community level, the relationship was negative for some taxa, for example surgeonfishes (Acanthuridae), one of the most abundant reef fish families. This demonstrates that the β-diversity-stability relationship should not be indiscriminately assumed for all taxa, but that a species' risk of extirpation in response to disturbance is likely to be taxon specific and trait based. By combining predictions of spatial and temporal turnover across the study area with observations in marine-protected areas, we conclude that protection alone does not necessarily confer temporal stability and that taxon-specific considerations will improve the outcome of conservation efforts.