Search

Around the world, coral reefs are in decline. Recent interest has focussed on the impacts of global warming/climate change, but the decline started long before the influence of climate change became apparent, driven by anthropogenic factors such as sedimentation, nutrient increase, and overfishing. These continue with no real signs of abatement, as does concomitant reef damage. The Persian Gulf supports widespread coral growth, especially on the Iranian side. Responding to issues of food security, the Iranian government has proposed large-scale aquaculture (open-net fish pens) along their coastline, with an eventual production of 200,000 t/year. Nutrient discharge will be a major issue. We developed a hydrodynamic circulation model for the Persian Gulf which allows us to follow the path of dissolved material. We estimated the amount of nitrogen that would be produced by the projected farms and modelled nitrogen distribution over time, using production rates of 44kgN released/t of fish. In a model run simulating one year at full operation of the proposed number of fish farms, we estimate that most of the reefs on the Iranian side will be bathed in waters with nutrient levels higher than will allow for reef survival. We used a trigger value of 20 μg/l total N. Mangroves will also be affected. There is significant trans-border movement of nutrients, to the waters of neighbouring countries. In fact, withing a few years the entire Gulf will be affected. These planned aquaculture projects have the potential to damage the mangroves and kill every reef in the Persian Gulf in a very short period of time. There is a high probability of affecting fisheries resources in neighbouring countries-a situation to be avoided in politically volatile regions. There seem only two solutions: 1. either run the fish farms so that nutrient discharge is kept to acceptable levels, using an ironclad monitoring system, or 2. bring the operations on land by establishing recirculating aquaculture systems.

Aliwal Shoal lies south of Durban in South Africa and has been the subject of recent bathymetric, seafloor and benthic surveys. ANOVA of the biological data revealed that the biota were uniformly distributed on the reef with the exception of encrusting sponges and algae on rock. The variations in distribution of these biota were significant and, in the case of the encrusting sponges, appeared to be related to the discharge of a wood pulp effluent. Further evidence of this was suggested by stable isotope analyses of representative organisms. The encrusting sponges were recommended as good candidates for further monitoring of the effects of the wood pulp effluent on Aliwal Shoal as the effluent pipeline has been extended.

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'.

The 15N content of tissue from the coral Porites lobata was enriched, relative to corals from reference sites, at 5 of 7 Indo-Pacific sewage-affected reefs. Enrichment was as high as 3.7‰. The δ13C of sewage-affected corals suggests they maintained a high degree of autotrophic nutrition. 15N-enriched wastewater dissolved inorganic nitrogen (DIN), derived from untreated sewage, is the most likely cause for enrichment in coral tissue 15N, though changes in coral nutrition, metabolism and zooxanthellae population dynamics are possible additional factors. Isotopic measurements of coral tissue can provide a simple means of detecting wastewater uptake by corals.

Massive coral growth rates may be poor indicators of coral reef health where coral reefs are subject to combined eutrophication and sedimentation. Massive coral growth (vertical extension) rates on polluted reefs were not different from extension rates on unpolluted reefs, while live coral cover was low and bioerosion intensity high, leading to net reef erosion and death of the polluted reefs. These combined patterns of coral growth rates, coral cover and bioerosion were documented on reefs affected by land-based pollution in the Java Sea, South Sulawesi and Ambon, Indonesia. Acid-insoluble content in coral skeletons reflected land-based pollution stress on reefs more reliably than did coral extension rates. Coral skeletal density was lower on polluted Java Sea reefs than on unpolluted reefs used as reference sites, but coral calcification rates were not significantly different. The most eutrophied Java Sea reefs had net carbonate loss, indicating net reef erosion, while a fringing reef adjacent to mangroves and two unpolluted coral cays both had positive net carbonate production. Coral growth and reef growth were decoupled, in that coral growth rates did not reliably predict rates of reef accretion. The apparently paradoxical combination of normal to rapid coral growth and net reef erosion on polluted reefs illustrates the need for a whole-reef perspective on coral reef health.

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.

Effective tools for monitoring the status of ecological restoration projects are critical for the management of restoration programs. Such tools must integrate disparate data comprised of multiple variables that describe restoration status, including the condition of environmental stressors, landscape connectivity, ecosystem resilience, and ecological structure and function, while communicating these concepts effectively to a wide range of stakeholders. In this paper we describe the process of constructing multimetric indices (MMIs) for monitoring restoration status for restoration projects currently underway on the eastern coast of Saudi Arabia. During this process, an initial suite of measurements is filtered for response and sensitivity to ecosystem stressors, eliminating measurements that provide little information and reducing future monitoring efforts. The retained measurements are rescaled into comparable domain metrics and assembled into MMIs. The MMIs are presented in terms of established restoration theories, including restoration trajectory and restoration endpoint targets.

While coral reefs decline, scientists argue, and effective strategies to manage land-based pollution lag behind the extent of the problem. There is need for objective, cost-effective, assessment methods. The measurement of stable nitrogen isotope ratios, delta(15)N, in tissues of reef organisms shows promise as an indicator of sewage stress. The choice of target organism will depend upon study purpose, availability, and other considerations such as conservation. Algae are usually plentiful and have been shown faithfully to track sewage input. The organic matrix of bivalve shells can provide time series spanning, perhaps, decades. Gorgonians have been shown to track sewage, and can provide records potentially centuries-long. In areas where baseline data are lacking, which is almost everywhere, delta(15)N in gorgonians can provide information on status and trends. In coral tissue, delta(15)N combined with insoluble residue determination can provide information on both sewage and sediment stress in areas lacking baseline data. In the developed world, delta(15)N provides objective assessment in a field complicated by conflicting opinions. Sample handling and processing are simple and analysis costs are low. This is a method deserving widespread application.

Bioerosion by Cliona delitrix and Cliona lampa was assessed at 43 sites along the Florida Reef Tract, USA, in the summer of 2001. Sponge abundances were estimated using rapid visual assessment. Tissue samples of sponges were taken for analysis of d 15 N. Comparison samples were taken from Belize. Annual trends in sponge abundance were estimated from archived videos covering the period from 1996 to 2001. Sites with the greatest boring sponge size and cover were in the Backcountry and Lower Keys, where total nitrogen, ammonium, and d 15 N levels were highest. The sites with the largest relative increase of C. delitrix and C. lampa over the 5 year period were in the Upper Keys, where the greatest relative decline in stony coral cover has occurred. Florida sponge d 15 N values were 5.2(±0.1)%, suggesting the influence of human waste; in comparison, offshore Belize samples were 2.1(±0.1)%. These results suggest sewage contamination of the Florida Reef Tract, shifting the carbonate balance from construction to destruction. � 2005 Elsevier Ltd. All rights reserved.

Concrete cinder blocks and Pleistocene coral limestone rubble were submerged in the East Back Reef lagoon at Discovery Bay, Jamaica for 13 years. In 1986, they were collected, slabbed, and examined for bioeroding infauna. Taxa varied in their ability to penetrate the non-calcareous cement matrix. Polychaetes and the bivalve, Lithophaga, bored all substrata easily, although the polychaetes preferred the cement. The sponges, Cliona and Damiria, only occurred in calcium carbonate aggregate and thus were limited to superficial attack. Results indicate that concrete structures in tropical and sub-tropical seas are subject to the same bioerosive forces as any carbonate substrates. Moreover, the two genera which were more abundant in concrete, Lithophaga and Cliona, are circum-global bioeroders which are more destructive in areas of high productivity and eutrophication. These environments are found in areas of marine construction activity.