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 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.