Biological Community in Submerged Caves and Marine Lakes in ha Long-Cat Ba Area, Vietnam

Abstract

Submerged caves and marine lakes are two iconic and common ecosystems in Ha Long-Cat Ba area. However, their biological characteristics are poorly known since very limited studies have been conducted. The aim of this study was to investigate biodiversity in these ecosystems. Three submerged caves (Hang Sang, Hang Toi and Qua Bang) and three marine lakes (Dau Be, Ang Du and Qua Bang) were chosen for study. The results showed that organism communities in submerged caves were abundant with over 142 species found. The popular groups comprised sponge and soft coral which were distributed along the length of the caves. Several species with high economic value were widespread in the caves, including stone crab Myomenippe hardwickii, flower crab Portunus pelagicus, cone snails Trochus pyramis, shoemaker spinefoot Siganus sutor, snapper Lutjanus russellii. Species that permanently live in caves were not detected. In the lakes where water is well exchanged to the sea, coral reefs were found and they usually formed a narrow band around the lakes. Sandy beaches were often observed around the lakes at the depths of 0.5-2 m, containing specialty species as clam (Sanguinolaria diphos), snout otter clam (Lutraria rhychaena), sea cucumbers with high density (in Dau Be, Qua Bang). There was no coral reef in the enclosed lake (Ang Du) because of low salinity.

Stony Corals and Their Associated Fauna Residing in Marine Lakes under Extreme Environmental Conditions

“…Colin [5] reported on coral communities in Palau's Heliofungia Lake and displayed images of a dense cover of free-living Heliofungia actiformis, as well as encrusting corals with large populations of Septifer mussels growing on them, and a foliose coral (Echinopora lamellosa) growing on a slope of the lake. In Ha Long Bay (Vietnam), four marine lakes have been reported to have coral, although specific species were not mentioned: Lake Dau Be (with a narrow strip of coral reef distributed sparsely around the lake), Lake Qua Bang (narrow strip of corals), Lake Bui Xam (a belt of massive corals), and Hang Du II Lake (the rocky shores of the lake are partially covered by a belt of corals) [38,39]. In Indonesia, Tomascik and Mah [40] reported the coral Alveopora tizardi from the marine Kakaban Lake in East Kalimantan province.…”

“…species were not mentioned: Lake Dau Be (with a narrow strip of coral reef distributed sparsely around the lake), Lake Qua Bang (narrow strip of corals), Lake Bui Xam (a belt of massive corals), and Hang Du II Lake (the rocky shores of the lake are partially covered by a belt of corals) [38,39]. In Indonesia, Tomascik and Mah [40] reported the coral Alveopora tizardi from the marine Kakaban Lake in East Kalimantan province.…”

Marine biodiversity in Ha Long bay and Cat Ba archipelago

“…Some environmental factors of limestone lakes in Ha Long bay -Cat Ba archipelago (Ngai, N. D., et al,[8] with modifications)…”