Coral reefs and marine resources are culturally, as well as economically, vital to Pohnpei, situated in the Federated States of Micronesia (FSM). Farming and fishing are the main sources of livelihood for most Pohnpeian communities. Pohnpei has eleven Marine Protected Areas (MPAs) where nine are situated in the Pohnpei Island Lagoon and two MPAs on the outer low-lying atolls. Like many other Pacific Island countries Pohnpei is on the verge of creating more MPAs. However, the marine environment continues to be significantly threatened by human and natural influences. The recognised threats are yet to be methodically investigated.
This thesis used a combination of sediment, coral, fish, climatic, and oceanographic data, and focused on the Pohnpei Lagoon, examining a range of natural and human issues in the marine environment both at the local level (focusing on that within the Pohnpei Lagoon) and regional level (focusing on the western Pacific region).
Evidence from historical, archaeological, and modern experience has influenced various marine impacts that have altered the coastline and the marine environment of the Pohnpei Lagoon. Humans have greatly impacted on the coral diversity and fish populations in the Pohnpei Lagoon by over-fishing and contributing to accelerated sediment inputs. My study findings shows that that increased sea surface temperature (SST) caused by El Ni o events is not the only cause of coral bleaching, but also cooling of SST, and other human factors. However, when corals bleach they recover by symbiont shuffling . This is an ingenious way in which corals host one or more varieties of their zooxanthelle (Symbiodinium symbiont clades) that are more tolerant of the stress caused by increased SST and human factors.
The recognised natural climatic variability, particularly the El Ni o/Southern Oscillation (ENSO), may pose a significant threat to the Pohnpei Lagoon. El Ni o events are associated with: a change in trade winds and stronger wind gusts attributed to typhoons; lower rainfall causing drought; a decrease in SST attributed to cooling of the marine environment; increase of salinity in marine estuaries affecting development and recruitment of marine species communities; and a steep fall in sea level exposing corals to other elements. The various on-going human threats and El Ni o-like conditions have caused giant clams (Tridacna gigas) to become extinct, have endangered herbivorous fish populations, and caused coral bleaching by cooling of SST.
Although high SSTs are normally blamed for coral bleaching, the last major bleaching event in Pohnpei (2002) was likely to be due to a reduction in salinity (freshwater runoff and lower sea level), and there has been strong recovery. However, decreasing water temperatures rather than increases of SSTs may contribute to coral bleaching in the Pohnpei Lagoon and the Micronesian region. The Micronesian region appears to have suffered relatively few episodes of regional coral bleaching events. This is due to the Western Pacific Warm Pool (WPWP) where sea surface temperatures exceed 29 C but also where various feedback mechanisms limit the maximum SSTs.
The management aims of Pohnpei's MPAs are to move forward, while still respecting traditional practices. However, a lack of scientific monitoring, technical support and funding restricts our understanding of human and natural influences on the existing MPAs and the Pohnpei Lagoon. With respect to our policy makers the findings of the present research have implications on the future work in Pohnpei's marine environment and for policy makers, to make more-informed decisions before establishing new MPAs.
My key recommendations were: 1.) Integrate coral and fish monitoring during and after El Ni o events to understand El Ni o effects on the Pohnpei environment. 2.) Undertake herbivorous fish investigation into their populations inside and outside the MPAs. 3.) Do not cut down vegetation along coastline areas, as it prevents erosion 4.) Investigate Symbiodinium coral clades in Pohnpei Lagoon and the outer low-lying atolls.
