Mactan Research Articles

TYPHOON HAZARD ANALYSIS OF THE CEBU-CORDOVA LINK EXPRESSWAY ACROSS MACTAN CHANNEL

The Cebu-Cordova Link Expressway (CCLEX) is an inter-island bridge that links Cebu City to Mactan Island through the municipality of Cordova. The 8.9-km-long structure spans from the Cebu South Coastal Road (CSCR), crosses the Mactan Channel and Mactan Reef Flat, then connects to a causeway in Barangay Pilipog in Cordova. It is the longest and tallest bridge in the Philippines as of 2022. The channel is approximately 12-km-long strait bound to the northwest by Cebu Island and to the southeast by Mactan Island. Both ends of the channel are approximately 0.5 km wide. Adjacent to the southwest end of the channel is the Mactan Reef Flat. It is a 3,000-hectare expanse of mangroves, corals, and seagrass. CCLEX, with its local features, consisting of causeways, viaducts, pylons with pile foundations, piers, bridges, tidal inlets, and a toll plaza, is found to have affected the wave climate within the Mactan Channel and Mactan Reef Flat during extreme typhoons. This paper presents the analyses and synthesis of the effects of the CCLEX substructure on the extreme hazards of storm tide and typhoon waves of typhoons that tracked Mactan Channel.

Description of a new moray eel (Anguilliformes: Muraenidae) from the Philippines, with a preliminary assessment of genetic and morphological variations of the Uropterygius concolor species complex.

Uropterygius concolor Rüppell, the type species of the genus Uropterygius, is a small, uniformly brown moray considered to be widely distributed in the Indo-Pacific region. However, a recent study indicated that the real U. concolor is currently known only from the type locality in the Red Sea, and species recorded outside the Red Sea may represent a species complex that comprises several species. In this study, we assess the genetic and morphological variations of this species complex based on available data. Analyses of cytochrome c oxidase subunit I sequences revealed at least six distinct genetic lineages recognized under 'U. concolor'. After carefully comparing the morphologies, one of the lineages is described herein as a new species, Uropterygius mactanensis sp. nov., based on 21 specimens collected from Mactan Island, Cebu, Philippines. Another distinct lineage is considered to be a possibly undescribed species based on diagnostic morphological characters. Although the taxonomic status of junior synonyms of U. concolor and some lineages still remain unresolved, this study provides informative morphological characters (i.e., tail length, trunk length, vertebrae number, and arrangement of teeth) that can be used in future studies on this species complex.

A new distributional record of the black coral Antipathes cf. griggi in Mactan Island, Philippines.

The black coral Antipathes cf. griggi was reported for the first time outside the Hawaiian Archipelago. This short report provides details and short description of the newly recorded species in Mactan Island, Philippines.

Gathering Internal Organs of the Wedge Sea Hare (Dolabella auricularia): A Case on Mactan Island, Cebu, the Philippines

Gathering Internal Organs of the Wedge Sea Hare (Dolabella auricularia): A Case on Mactan Island, Cebu, the Philippines

Oil degrading and heterotrophic bacteria composition in the oil-spilled affected mangrove forest sediment in Mactan Island, Central Philippines

Oil spill increases the amount of hydrocarbons in marine ecosystems that disrupts the ecological balance with severe economic consequences. This study was conducted to assess the microbial composition in the sediments of oil affected areas in Mactan Island, Cebu eight months after the incident. Four sites designated as S1 (low) , S2 (mid) and S3 (high) representing oil spill contamination gradient were established. A reference site (Ref) was selected. Sediment samples from each site were collected for microbial count enumeration (heterotrophic and oil degrading bacteria) using the spread plate technique and the MPN method respectively. An increasing pattern of heterotrophic bacteria and decreasing trend of oil degrading bacteria counts were observed along S1, S2 and S3. Results revealed the heterotrophic bacteria count in all sites did not vary significantly. In addition, Ref exhibited highest and lowest count for heterotrophic and oil degrading bacteria respectively whereas S3 and S2 displayed highest in density for the oil degrading bacteria. The proliferation of oil degrading microbe implies the possible presence of oil residues including those PAH components that gets more toxic through time.

Population genetic structure of the messmate pipefish Corythoichthys haematopterus in the northwest pacific: evidence for a cryptic species

The population genetic structure of the messmate pipefish, Corythoichthys haematopterus, in the northwest Pacific was investigated based on the partial mitochondrial DNA cytochrome b (589 bp) and 16S rRNA (528 bp) region sequences of 108 individuals collected from six sites along the coast of the Japanese archipelago and one site on Mactan Island, the Philippines. A total of 60 and 28 haplotypes were obtained from the cytochrome b and 16S rRNA regions, respectively. Two genetically distinct lineages were detected: lineage A and B, which are separated by mean pairwise genetic distances of 23.3 and 14.1% in the partial cytochrome b and 16S rRNA genes, respectively. Such a huge genetic divergence between lineages, which is comparable to or even higher than the interspecific level, and the difference in their geographical distributions and habitat preferences suggests that they are distinct species, although there is no marked difference in their morphology. Haplotype network and gene and nucleotide diversity statistics indicate that the two lineages have different biogeographic histories: lineage A experienced rapid population expansion after a population bottleneck whereas lineage B has a long evolutionary history in a large stable population. In contrast, the levels of genetic variation among populations are relatively low in both lineages, probably because of frequent gene flow among populations resulting from the dispersal of pelagic larvae by the Kuroshio Current. These results indicate that past climatic events and contemporary oceanographic features have played a major role in establishing the population genetic structure of C. haematopterus.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-2-408) contains supplementary material, which is available to authorized users.

Spatial distribution of heavy metals in surface sediments of a mangrove creek and its adjacent seagrass bed (Cordova, Mactan island, central Philippines)

Spatial distribution of heavy metals in surface sediments of a mangrove creek and its adjacent seagrass bed (Cordova, Mactan island, central Philippines)

Imposex in <i>cronia margariticola</i> (Mollusca, Prosobranchia) as a potential marine pollution biomonitor around Mactan island, central Philippines

Imposex in <i>cronia margariticola</i> (Mollusca, Prosobranchia) as a potential marine pollution biomonitor around Mactan island, central Philippines

Correlation of inorganic nutrients to the standing crop of “green tide” algae during the peak growth season in eastern Mactan island, central Philippines

Correlation of inorganic nutrients to the standing crop of “green tide” algae during the peak growth season in eastern Mactan island, central Philippines

A new species of Lissocidaris (Echinodermata: Echinoidea: Cidaridae) from the Philippines: convergent evolution among smooth-spined cidaroids

Lissocidaris xanthe sp. nov. Coppard & van Noordenburg, 2007 occurs at depths of between 150 m and 250 m near Mactan Island in the Philippines. It is distinctive in having aboral interambulacral spines that measure more than twice the test’s horizontal diameter at the ambitus. The neck of each spine is typically white and unconstricted. Oral primary interambulacral spines have serrated edges. Large globiferous pedicellariae have moderately narrow valves, each valve with a narrow longitudinally oval opening beneath a large terminal tooth. It is similar to the type species of Lissocidaris (L. fusca) in having smooth, aboral interambulacral spines, the smooth surface formed by dense, anastomosing cortical hairs that coalesce to form a continuous crust between longitudinal ridges. Smooth spines are also found in two other cidaroid genera: Calocidaris and Compsocidaris. However, in these genera, the glossy surface results from the cortex being devoid of hairs; this provides a marked example of convergent evolution.

Taxonomic and ecological profile of `green tide' species of Ulva (Ulvales, Chlorophyta) in central Philippines

Ulva spp. are common in the intertidal zones of the Philippines, but, at certain times, could over-proliferate producing blooms or ‘green tide’ in some protected bays. In Mactan Island (Cebu), central Philippines, at least two species constitute the Ulva population, either as free-living or attached form. The one referred to in the literature as ‘Ulva lactuca’ mainly consists of free-living population while the species referred to as Ulva reticulata consists mainly of attached population. Based on morphological and physiological characteristics, ‘U. lactuca’ differs much from the descriptions of the species from its type locality in Europe in having a crumpled texture of blade, presence of tooth-like protuberances at the margins, thinner thallus (40–50 μm) and more pyrenoids per cell (two to four). The species referred to as ‘ U lactuca’ in the Philippines therefore is a different species. Two morphotypes consisted the ‘ U. lactuca’ population from Mactan — a thick thallus and a thin thallus type. However, both morphotypes cultured under the same condition in the laboratory could transform into the same thin-thallus type observed in the field. ‘Green tide’ caused by ‘ U. lactuca’ occur almost regularly in Station 1 of Mactan Island, reaching an average biomass of up to 2.6 kg wet wt m−2 (or 0.5 kg dry wt m−2). Ulva reticulata, although was less abundant in the rocky tidal zone at most times, reaching an average biomass of only up to 0.15 kg wet wt m−2 (or 0.03 kg dry wt m−2) had caused green tide in Station 2 around February-March. Reproductive structures were not observed in both Ulva species during the survey period suggesting that vegetative fragmentation is the main mode of propagation. Vegetative tissues excised from the thallus can be induced to release biflagellated large and small zooids.

Feeding, respiration, and excretion by the tropical sea urchin Tripneustes gratilla (Echinodermata: Echinoidea) from the Philippines

The rates of ingestion, egestion, ammonium excretion, and CO2 respiration of Tripneustes gratilla (Echinodermata: Echinoidea) from a shallow water embayment at eastern Mactan Island, central Philippines were examined. There was no significant difference in weight-specific feeding rate with the three macrophytes (Sargassum polycystum, Thalassia hemprichii, and Kappaphycus alvarezii). The power function equation, M=KWb fitted well with the weight-specific egestion rates ((r2=0·93), weight-specific CO2 respiration rates (r2=0·92) and ammonium excretion rates (r2=0·86). Weight-specific egestion rates, CO2 respiration and ammonium excretion were indirectly proportional to body weight. For weight-specific egestion rate (in μg DW faeces/g DW urchin-h), the regression coefficient, b and constant, K were −2·31±0·68 (mean±SE) (P=0·02) and 6359·55±5394·31 (P=0·29), respectively. The b and K for CO2 respiration were −1·28±0·48 (P=0·04) and 39·72±10·59 (P=0·01), respectively. For ammonium excretion, the b and K were −1·03±0·46 (P=0·11) and 262·51±56·89 (P=0·02), respectively.

Adaptive use of a rock coast for tourism — Mactan Island, Philippines

Cebu and the adjacent limestone island of Mactan constitute the second most popular tourist destination in the Philippines after Manila. The more exposed southeast side of Mactan has a low rock coast with limited sandy beaches and two lagoons. Since the 1970s, this coast has experienced significant change due to resort development. Based on a survey of the resorts, three types of modification to the rock coast can be identified. The early stage of modification involved the least amount of change to the rock coast. The existing limited sandy beaches were used and sea walls were built where necessary. The middle stage of modification witnessed a variety of coastal structures built to retain the beaches, together with the use of imported sand for beach nourishment. Groins and breakwaters were deployed in various ways to create different resort layouts. The final stage of modification was the excavation of the rock coast and the creation of new and artificial beaches. Mactan's experience shows the potential of low rock coasts for tourism development. The typology of change to the rock coast can be considered as limited, localized and effective modification of the rock coast for resorts. Such uses tend to result in, and reinforce, the enclave character of tourism development along a rock coast, which differs from the prevalent ribbon pattern of tourism development along sandy beaches.

Mactanamide, A New Fungistatic Diketopiperazine Produced By A Marine Aspergillus Sp

Mactanamide (1), a new diketopiperazine containing the uncommon amino acid D-2,6-dihydroxyphenylalanine, has been isolated from the mycelium of an undescribed marine fungus of the genus Aspergillus. the new fungal strain was obtained from the surface of the brown marine alga Sargassum sp. collected near Mactan Island in the Philippines. the structure and absolute stereochemistry of 1 was determined by interpretation of spectral data, by comparison with model compounds, and by measurement of the CD spectra of its component amino acids.

On the abundance and activity pattern of zoobenthos inhabiting a tropical reef area, Cebu, Philippines

A benthic faunal study was carried out in the tidal area of Mactan Island (Cebu, Philippines). The area was subdivided along a transect from the beach to the reef according to benthic assemblages. The sediments are largely composed of calcareous skeletal remains of the indigenous biota and surrounding calcareous rocks. The content of protein and carbohydrates of the sediment was estimated, providing an approximation of organic matter in terms of feeding efficiency. Total number of zoobenthos, both as regards the sediment samples and as to the epifaunal communities associated with seaweeds, is rather uniformly distributed justifying the 95% confidence level (P>0.05). Distinct differences are apparent in abundance values of individual taxa. Although the study area showed the expected distribution pattern, with dominance of Nematoda (39%) living in sediment and Harpacticoida (36–66%) dwelling on Thalassia and algae, Polychaeta reveal a dominant attraction to both these habitats. The reasons for this phenomenon are discussed in relation to the absolute lack of macrofaunal predators The zoobenthos adjust their distribution and activity to fluctuating conditions of the environment. Light is mainly suggested as stimulating diel migration activities of the benthic fauna, moving upwards from the sediment to the algae and Thalassia during daytime. In a field experiment the zoobenthos was investigated for digestion activity over a diurnal cycle. The results reveal that feeding activity of zoobenthos follows a diel cycle showing maximum activity during the morning and evening obviously influenced by changes of light.

Reproductive Behavior and Social Organization of the Pomacanthid Fish Genicanthus lamarck at Mactan Island, Philippines

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Part four: Leprosy and Assortative mating on Mactan Island, Philippines

Abstract A social stigma on leprosy has often elicited patterns of positive assortative mating with regard to the presence of the disease in a spouse or in his relatives. Mating patterns were analyzed in a Philippine population in which leprosy has been endemic for over a century. A clear pattern of negative assortative mating was observed after 1915 and became more pronounced through time. Some possible causes and consequences of this mating pattern are discussed.