Community structure of Quaternary coral reefs compared with recent life and death assemblages

Abstract.-This paper assesses the reliability with which fossil reefs record the diversity and community structure of adjacent Recent reefs. The diversity and taxonomic composition of Holocene raised fossil reefs was compared with those of modern reef coral life and death assemblages in adjacent moderate and low-energy shallow reef habitats of Madang Lagoon, Papua New Guinea. Species richness per sample area and Shannon-Wiener diversity (HЈ) were highest in the fossil reefs, intermediate in the life assemblages, and lowest in the death assemblages. The taxonomic composition of the fossil reefs was most similar to the combination of the life and death assemblages from the modern reefs adjacent to the two fossil reefs. Depth zonation was recorded accurately in the fossil reefs. The Madang fossil reefs represent time-averaged composites of the combined life and death assemblages as they existed at the time the reef was uplifted. Because fossil reefs include overlapping cohorts from the life and death assemblages, lagoonal facies of fossil reefs are dominated by the dominant sediment-producing taxa, which are not necessarily the most abundant in the life assemblage. Rare or slow-growing taxa accumulate more slowly than the encasing sediments and are underrepresented in fossil reef lagoons. Time-averaging dilutes the contribution of rare taxa, rather than concentrating their contribution. Consequently, fidelity indices developed for mollusks in sediments yield low values in coral reef death and fossil assemblages. Branching corals dominate lagoonal facies of fossil reefs because they are abundant, they grow and produce sediment rapidly, and most of the sediment they produce is not exported. Fossil reefs distinguished kilometer-scale variations in community structure more clearly than did the modern life assemblages. This difference implies that fossil reefs may provide a better longterm record of community structure than modern reefs. This difference also suggests that modern kilometer-scale variation in coral reef community structure may have been reduced by anthropogenic degradation, even in the relatively unimpacted reefs of Madang Lagoon. Holocene and Pleistocene fossil reefs provide a time-integrated historical record of community composition and may be used as long-term benchmarks for comparison with modern, degraded, nearshore reefs. Comparisons between fossil reefs and degraded modern reefs display gross changes in community structure more effectively than they demonstrate local extinction of rare taxa

Local ecological knowledge and multidisciplinary approach lead to discovery of hidden biodiversity in the deep ocean of Labrador, Canada

nternational commitments to preserve global biodiversity target the protection of 30% of marine habitats by 2030. The lack of even basic knowledge of many marine areas (e.g., deep oceans) combined with short timelines require integrative knowledge and multidisciplinary techniques to be used to efficiently identify areas worthy of protection. Here we outline a case study of the discovery of the Makkovik Hanging Gardens found in a deep-water trough in coastal Labrador, Canada. The area is of ecological significance because it supports high densities of vulnerable marine ecosystem indicator taxa, including the gorgonian coral Primnoa resedaeformis on portions of its vertical submarine walls. This study illustrates the exploratory process initiated by Nunatsiavut, which integrated local knowledge, scientific models, and a variety of technologies (such as remotely operated vehicles and multibeam sonar) to discover deep-water hidden biodiversity toward the advancement of both local Indigenous and global conservation goals

Loss of coral reef growth capacity to track future increases in sea level

Water-depths above coral reefs is predicted to increase due to global sea-level rise (SLR). As ecological degradation inhibits the vertical accretion of coral reefs, it is likely that coastal wave exposure will increase but there currently exists a lack of data in projections concerning local rates of reef growth and local SLR. In this study we have aggregated ecological data of more than 200 tropical western Atlantic and Indian Ocean reefs and calculated their vertical growth which we have then compared with recent and projected rates of SLR across different Representative Concentration Pathway (RCP) scenarios. While many reefs currently show vertical growth that would be sufficient to keep-up with recent historic SLR, future projections under scenario RCP4.5 reveal that without substantial ecological recovery many reefs will not have the capacity to track SLR. Under RCP8.5, we predict that mean water depth will increase by over half a metre by 2100 across the majority of reefs. We found that coral cover strongly predicted whether a reef could track SLR, but that the majority of reefs had coral cover significantly lower than that required to prevent reef submergence. To limit reef submergence, and thus the impacts of waves and storms on adjacent coasts, climate mitigation and local impacts that reduce coral cover (e.g., local pollution and physical damage through development land reclamation) will be necessary

Reef degradation and coral biodiversity in indonesia: Effects of land based pollution, destructive fishing practices and changes over time

Species-area curves calculated from line-intercept transect surveys on 15 reefs in three regions of Indonesia allow estimation of the relative decrease in within-habitat coral species diversity associated with different types of reef degradation. Reefs subject to land-based pollution (sewage, sedimentation, and/or industrial pollution) show 30–50% reduced diversity at 3 m, and 40–60% reduced diversity at 10 m depth relative to unpolluted comparison reefs in each region. Bombed or anchor damaged reefs are ca 50% less diverse in shallow water (3 m depth) than are undamaged reefs in the same region, but at 10 m depth the relative decrease is only 10%. Comparison reefs in the Java Sea are ca 20% less diverse than their counterparts in Ambon, Maluku. The results, compared with a previous survey in the Spermonde Archipelago found a 25% decrease in generic diversity of corals on two reefs resampled after 15 years. The decreased diversity on reefs subject to land-based pollution implies a dramatic, rapid decrease in Indonesian reef-based fisheries resources

Effect of Land-based Pollution on Central Java Coral Reefs

Land-based pollution has severely damaged nearshore corals reefs in the Jepara area, Central Java. Effect described here include reduced coral cover and diversity, high coral mortality, reduced reef habitat complexity, and increased bioerosion intensity, compared to reference reefs in the Karimunjawa Islands National Marine Park, Central Java. Furthermore, the polluted reefs have negative net carbonate production indicating net reef erosion. Reef health parametres based on coral cover and diversity and on net carbonate production are inversely correlated with chlorophyll A concentration, suggesting eutrophication of coastal waters as a key agent of reef degradation. Untreated sewage dumping, agricultural runoff, and aquacultural effluent all contribute to nearshore eutrophication in Central Java, but it is not possible from this study to determine which of these types of land-based pollution is most responsible for degradation of Central Java reefs. Efforts to restore the condition of degraded reefs must begin with controlling sources of land-based pollution

Ichnodiversity in the eastern Canadian Arctic in the context of polar microbioerosion patterns

Studies of marine microbioerosion in polar environments are scarce. They include our recent investigations of bioerosion traces preserved in sessile balanid skeletons from the Arctic Svalbard archipelago and the Antarctic Ross Sea. Here, we present results from a third study site, Frobisher Bay, in the eastern Canadian Arctic, together with a synthesis of our current knowledge of polar bioerosion in both hemispheres. Barnacles from 62 to 94 m water depth in Frobisher Bay were prepared using the cast-embedding technique to enable visualization of microboring traces by scanning electron microscopy. In total, six ichnotaxa of traces produced by organotrophic bioeroders were found. All recorded ichnotaxa were also present in Mosselbukta, Svalbard, and most in the Ross Sea. Frobisher Bay contrasts with Mosselbukta in that it is a siliciclastic-dominated environment and shows a lower ichnodiversity, which may be accounted for by the limited bathymetrical range and a high turbidity and sedimentation rate. We evaluate potential key ichnotaxa for the cold-temperate and polar regions, of which the most suitable are Flagrichnus baiulus and Saccomorpha guttulata, and propose adapted index ichnocoenoses for the interpretation of palaeobathymetry accordingly. Together, the three studies allow us to make provisional considerations about the biogeographical distribution of polar microbioerosion traces reflecting the ecophysiological limits of their makers

Bioerosion of Live Massive Corals and Branching Coral Rubble on Indonesian Coral Reefs

The degree of bioerosion of live massive corals and rubble from branching corals were measured on nine reefs from two regions of Indonesia: the Java Sea and Ambon. Bioerosion in massive corals was measured by collecting live corals, cutting and X-raying slabs, and measuring the cross-sectional area removed from each slab by the various bioeroding organisms. A technique analysing branching coral rubble was developed and similarly used to evaluate the degree of bioerosion on the reefs. This rubble technique has potential advantages over the massive coral technique since it does not require the expense and technical expertise of making and analysing X-rays, nor does it require the destruction of living coral heads. The effectiveness of this rubble technique is evaluated here. Levels of bioerosion in massive coral heads and rubble from branching corals are each compared with environmental variables and health parameters of the nine reefs. Overall, both techniques showed that bioerosion levels were positively correlated with environmental variables indicative of eutrophication. Bioerosion of live massive corals and of branching coral rubble were positively correlated. At the Ambon sites, where the eutrophication levels differ only slightly compared to the Java sites, bioerosion in coral rubble was a more sensitive indicator of eutrophication stress than bioerosion measured from massive coral heads. The rubble technique we outline is a useful rapid reef assessment technique that could be a valuable contribution to the ‘reef survey toolbox'

Comparing Selections of Environmental Variables for Ecological Studies: A Focus on Terrain Attributes

<div><p>Selecting appropriate environmental variables is a key step in ecology. Terrain attributes (<i>e</i>.<i>g</i>. slope, rugosity) are routinely used as abiotic surrogates of species distribution and to produce habitat maps that can be used in decision-making for conservation or management. Selecting appropriate terrain attributes for ecological studies may be a challenging process that can lead users to select a subjective, potentially sub-optimal combination of attributes for their applications. The objective of this paper is to assess the impacts of subjectively selecting terrain attributes for ecological applications by comparing the performance of different combinations of terrain attributes in the production of habitat maps and species distribution models. Seven different selections of terrain attributes, alone or in combination with other environmental variables, were used to map benthic habitats of German Bank (off Nova Scotia, Canada). 29 maps of potential habitats based on unsupervised classifications of biophysical characteristics of German Bank were produced, and 29 species distribution models of sea scallops were generated using MaxEnt. The performances of the 58 maps were quantified and compared to evaluate the effectiveness of the various combinations of environmental variables. One of the combinations of terrain attributes–recommended in a related study and that includes a measure of relative position, slope, two measures of orientation, topographic mean and a measure of rugosity–yielded better results than the other selections for both methodologies, confirming that they together best describe terrain properties. Important differences in performance (up to 47% in accuracy measurement) and spatial outputs (up to 58% in spatial distribution of habitats) highlighted the importance of carefully selecting variables for ecological applications. This paper demonstrates that making a subjective choice of variables may reduce map accuracy and produce maps that do not adequately represent habitats and species distributions, thus having important implications when these maps are used for decision-making.</p></div

Changing dynamics of Caribbean reef carbonate budgets: emergence of reef bioeroders as critical controls on present and future reef growth potential

Coral cover has declined rapidly on Caribbean reefs since the early 1980s, reducing carbonate production and reef growth. Using a cross-regional dataset, we show that widespread reductions in bioerosion rates—a key carbonate cycling process—have accompanied carbonate production declines. Bioerosion by parrotfish, urchins, endolithic sponges and microendoliths collectively averages 2 G (where G = kg CaCO(3) m^−2 yr^−1) (range 0.96–3.67 G). This rate is at least 75% lower than that reported from Caribbean reefs prior to their shift towards their present degraded state. Despite chronic overfishing, parrotfish are the dominant bioeroders, but erosion rates are reduced from averages of approximately 4 to 1.6 G. Urchin erosion rates have declined further and are functionally irrelevant to bioerosion on most reefs. These changes demonstrate a fundamental shift in Caribbean reef carbonate budget dynamics. To-date, reduced bioerosion rates have partially offset carbonate production declines, limiting the extent to which more widespread transitions to negative budget states have occurred. However, given the poor prognosis for coral recovery in the Caribbean and reported shifts to coral community states dominated by slower calcifying taxa, a continued transition from production to bioerosion-controlled budget states, which will increasingly threaten reef growth, is predicted

Stable isotope ratios in seawater nitrate reflect the influence of Pacific water along the northwest Atlantic margin

The flow of Pacific water to the North Atlantic exerts a globally significant control on nutrient balances between the two ocean basins and strongly influences biological productivity in the northwest Atlantic. Nutrient ratios of nitrate (NO3-) versus phosphate (PO34-) have previously been used to complement salinity characteristics in tracing the distribution of Pacific water in the North Atlantic. We expand on this premise and demonstrate that the fraction of Pacific water as determined by NO3-:PO34- ratios can be quantitatively predicted from the isotopic composition of subeuphotic nitrate in the northwest Atlantic. Our linear model thus provides a critically important framework for interpreting delta N-15 signatures incorporated into both modern marine biomass and organic material in historical and paleoceanographic archives along the northwest Atlantic margin