León, R. de

Findings:

The main conclusion of this study is that the shallow, warm and saline back-water habitat which is continuing to increase in importance within Lac Bay is unable to support meaningful mangroves, seagrass or algal meadows, nor the key nursery species. As the natural process of land reclamation by mangroves carries on, the bay’s important nursery habitats will come under additional salinity stress and likely continue to decrease in coverage and quality at an accelerated rate.

Distribution of sea grass and algal beds in Lac Bay

• The valuable seagrass and mangrove habitats of Lac are currently trapped in an enclosed bay.
• High light-intensity and well-circulated shallow habitats that fringed the mangroves of the central bay have the richest assemblages with the highest biotic coverage.
• Isolated mangrove pools have the lowest total cover, species richness and biodiversity of all habitats.
• Biotic diversity and cover decrease towards the deeper parts of the bay.
• There is an alarmingly rapid invasion of the bay by the invasive seagrass H. stipulacea.

Fish species utilization of contrasting habitats in Lac Bay

• Fish community variables differ consistently among habitats and are influenced by the percent cover of seagrass vegetation or presence of mangrove-root structure.
• Mangrove fringe habitats are a premier habitat since multiple life stages of a variety of species showed highest densities there. Mangrove fringing open waters had highest overall fish densities and species diversity.
• The various vegetated sub-habitats all play a unique role for different size-classes of different fish species. 

Management Recommendations:

• Management action is needed to stem further erosion of nursery habitat quality and ensure that a tipping-point is not reached beyond which recovery may be difficult or impossible.
• Measures should be taken to help restore water depth and circulation to relieve the bay’s ecosystem of thermal and salinity stress caused by the shallow backwaters. This includes excavating accumulated erosional and biogenic sediments as well as dredging to restore former feeder channels by removal of mangrove overgrowth (as already started by Stinapa).
• Further studies to assess the impacts of the invasive seagrass H. stipulacea on the bay’s flora and fauna.

Abstract:

Although Bonaire’s coral reefs remain among the healthiest and most resilient in the Caribbean, this IUCN report based on the IUCN Resilience Assessment of Coral Reefs highlights some of the threats that exist to Bonaire’s coral reefs, and which could have serious implications for resilience to future climate change and other threats. The report identified recommendations for addressing the current threats, as well as high and low resilience sites.

The threats and recommendations identified include:

Coastal development and artificial beaches.
Recommendation: All coastal construction on Bonaire should be strictly regulated and follow the construction guidelines. The guidelines should become law in order to be enforced appropriately.

Leaching from septic tanks.
Recommendation: It is strongly recommended that Bonaire invest in appropriate sewage treatment facilities to improve water quality and increase the resilience of its valuable coral reefs. It is also recommended that a water quality monitoring program be set up and sustained.

Increasing damselfish populations.
Recommendation: It is recommended that the fishing of predatory fish species on Bonaire’s coral reefs be controlled and managed to a sustainable level to prevent population explosions of prey fish capable of modifying the reef habitat.

Trididemnum and Lobophora.
Recommendation: It is recommended that the populations of Trididemnum and Lobophora are closely monitored and the factors contributing to the unnatural abun- dance of these coral-overgrowing organisms should be studied and then eliminated.

Due to a variety of factors affecting resilience which were assessed using the IUCN methodology, sites were also ranked according to their overall resilience: 

It is noteworthy that sites with lowest resilience ratings (e.g. Chachácha) are those most impacted by coastal development, while sites with highest resilience ratings (e.g. Marine Reserve North, Playa Frans, Karpata, Margate Bay, Vista Blue and South Bay) are those furthest away and least impacted by coastal development. 

Data on beach debris and tar contamination is provided for 21 natural beach sites in Bonaire, Southeastern Caribbean. Transects amounting to a combined length of 991 m were sampled March–May 2011 and a total of 8960 debris items were collected. Highest debris and tar contamination were found on the beaches of the windward east-coast of the island where geometric mean debris concentrations (± approx. 70% confidence limits) were 115 ± 58 items m-1 and 3408 ± 1704 g m-1 of beach front. These levels are high compared to data collected almost 20 years earlier on the nearby island of Curaçao. Tar contamination levels averaged 223 g m-1 on windward beaches. Contamination levels for leeward west-coast beaches were generally two orders of magnitude less than windward beaches.