Settlement Patterns of Corals and other Benthos on Reefs with Divergent Environments and Disturbances Histories around the Northeastern Arabian Peninsula

Abstract

Larval supply is a principal factor determining the establishment, structure, and diversity of sessile benthic assemblages on coral reefs. Benthic reef communities in north-eastern Arabia have been subject to recurrent disturbances in recent years, and subsequent recovery will be, in part, driven by variation in the supply of available colonists. Using settlement tiles deployed seasonally over 1 year at eight sites encompassing three environmentally divergent regions (southern Arabian Gulf, the Musandam Peninsula in the Strait of Hormuz, and the Sea of Oman) we assessed spatial and seasonal variability in settlement of benthic reef organisms. There was strong spatial variation in composition of new colonists among regions, mainly driven by the high abundance of coralline algae in the Arabian Gulf, colonial ascidians on the Musandam Peninsula and barnacles in the Sea of Oman. Seasonal differences in composition of new colonists were less important than regional differences, with seasonal variation in settlement not consistent among regions. The number of corals settling to the tiles was low compared to those reported for other regions, with mean densities ranging from 0 corals m −2 year −1 in the Sea of Oman to 30 (± 0.6 SE) and 38 (± 0.5 SE) in Musandam and the Arabian Gulf, respectively. Peak coral settlement abundance in the Gulf occurred in summer and autumn and in Musandam in spring (averaging 82 and 70 settlers m −2 year −1 , respectively, during the peak settlement season). This work provides the first record of large-scale spatial and seasonal patterns of settlement in north-eastern Arabia and provides valuable information on the supply of settlers available to recolonize heavily disturbed reefs in this region. The extremely low rates of coral settlement suggest that these marginal reefs are likely to be extremely slow to recover from on-going and future disturbances.

Population genetic structure of a major reef-building coral species Acropora downingi in northeastern Arabian Peninsula

“…Acropora corals in the Gulf have undergone major mortality events in the past three decades, often with losses of over 90% cover, with populations currently at the brink of collapse (Riegl et al 2018). Alarmingly, juveniles of Acropora are mostly absent from the coral community (Bento et al 2017;Pratchett et al 2017), reducing possibilities of recovery. Acropora downingi has now largely been extirpated from shallow and nearshore environments in the southern Gulf, and only occurs around offshore islands and seamounts where temperatures are buffered by deeper surrounding waters (Burt et al 2013(Burt et al , 2016.…”

Coral Reefs of Abu Dhabi, United Arab Emirates: Analysis of Management Approaches in Light of International Best Practices and a Changing Climate

“…These comprise direct anthropogenic (Lokier and Fiorini, 2016) and climatic stressors (Hoey et al, 2016), as well as management issues (Grizzle et al, 2016). Similar to corals worldwide, UAE corals are witnessing a decline induced by environmental and climatic extreme events, and ongoing industrial and human activities (Bento et al, 2016;Bento et al, 2017). Increasing challenges and environmental threats related to the country's rapid economic development, e.g., waste generation and land reclamation (Alzaylaie and Abdelaziz, 2016), have created pressures on the environment resulting in action by the government in the form of policies and enforcement of mitigation plans to reduce potential negative environment impacts.…”

“…Land-based activities and unsustainable development practices such as sediment and nutrient overloading threaten UAE coral reefs (Bento et al, 2016(Bento et al, , 2017Hoey et al, 2016;Lokier and Fiorini, 2016). The reduction of pressures from land-based activity necessitates enhanced coastal planning and EIA studies; improved and continuous coordination between authorities for the land and the sea governance, such as the example of the ongoing collaboration between EAD and DPM; and enforcement of regulations that protect such fragile ecosystems.…”

Decline in oyster populations in traditional fishing grounds; is habitat damage by static fishing gear a contributory factor in ecosystem degradation?

“…Quadrat imagery was calibrated to the known distance at which the photos were taken 1m -Ansi (2008). This methodology was adopted from Carleton and Done (1995) and Bento et al, (2017) as it was particularly comprehensive with a mandatory 5,000 individual observations per site and total of 90,000 for the complete survey.…”