menu.header.image.unacom.logo
 

National Committee on Marine Sciences (NCMS)

Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/6

Browse

Filters

1988 - 198921990 - 19972

Settings

AGROVOC Keyword: search.filters.agrovoc.abundanceHas files: No

Search Results

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Macroinfaunal biomass and energy flow in a shallow reef flat of the northwestern Philippines
    Nacorda, Hildie Maria E.; Yap, Helen T. (Springer, 1996-12)
    Macrofaunal biomass of the Lucero reef flat in the northwestern Philippines accounted for 9 to 52% of total sediment organic matter, and did not exhibit any significant temporal trend. The polychaetes and crustaceans consistently alternated as biomass dominants; the latter group showed monthly and seasonal variations along with the chaetognaths, molluscs, chordates, and chelicerates, among the major groups (p<0.05). Faunal abundance correlated significantly with biomass. Salinity, mean sediment grain size, sediment heterogeneity, and total organic matter were found to significantly influence faunal biomass. The sandy substrate community was characteristically heterotrophic throughout the monitoring period, i.e., P/R<1. Hourly rates of net primary production (p n ) did not exhibit any significant diurnal pattern. Monthly comparisons yielded significant differences for estimates of daily gross primary production, P, and respiration, R. Values of P were relatively low, and ranged from 2240 (± 1526 S.D.) to 4890 (± 1377) mg O2 m−2 d−1 while R ranged from 3744 (± 1504) to 6879 (± 903) mg O2 m−2 d−1. R was lower during the dry warm months than the wet months. Multiple regression analyses indicate that primary production was a positive function of light intensity and temperature, and a negative correlate of salinity (adjusted R 2 = 0.2444, p< 0.05). Respiration (r) did not appear to relate with any environmental variable, with total macroinfaunal abundance nor with biomass. Results of the study suggest that other heterotrophic components of the sand community were probably responsible for most of the energy consumption, and that these may be dependent on external sources of organic matter.
  • No Thumbnail Available
    Structure and temporal dynamics of macroinfaunal communities of a sandy reef flat in the northwestern Philippines
    Nacorda, Hildie Maria E.; Yap, Helen T. (Springer, 1997)
    Temporal variation in macroinfaunal community structure was assessed from monthly monitoring of the sandy substrate of the Lucero reef flat in Bolinao, Pangasinan (northwestern Philippines) between November 1990 and November 1991. The community was composed of 98 taxa from 10 phyla and was consistently dominated by the polychaete family Syllidae (19–33% of monthly total abundance). Five polychaete and crustacean taxa co-dominated with the syllids and exhibited monthly shifts in dominance ranks. Overall, there was no significant change in the composition of the community after a year. Results of the study show that the temporal dynamics of the community was a function of the seasonality in salinity and of the relatively consistent nature of the substrate. Abundances of macroinfaunal crustaceans, chaetognaths, and molluscs fluctuated significantly over 12 months, and corresponded to the seasonal fluctuation in salinity. Total and polychaete abundances did not show significant monthly variation, but tended to be influenced by salinity changes. Densities of turbellarians, nemerteans, and echinoderms appeared homogeneous across 12 months, and correlated with the consistency of substrate structure in the reef flat over the experimental period. In addition, sipunculid numbers seemed to be supported by the stable amount of organic matter in the sandy substrate.
  • No Thumbnail Available
    A comparison of two benthic survey methods
    Mingoa, S. S. M.; Menez, L. A. B. (Springer, 1988)
    The belt transect and the flowmeter methods, used to survey sedentary benthic organisms, were compared based on abundance estimates of tridacnid clams in the Cagayan Islands, Philippines, in April 1985. Two-way ANOVA and chi-square tests (P<0.05) show that both methods recorded similar estimates for the number of clams (regardless of species), both methods gave similar estimates for the number of individuals per species, and one or both methods may be biased for certain sizes of clams. Individuals smaller than 6 cm shell length seemed to be underestimated by the flowmeter method. Future studies must investigate the size selectivity of the method used, for instance by conducting permanent belt, transect surveys of varied belt widths (e.g. 1, 1.5,2,2.5 m) and then comparing the recorded lengths of the most abundant clams. This will aid investigators to evaluate their data properly, and enable comparison of clam-stock estimates between surveys.
  • Thumbnail Image
    Status of giant clam resources of the Philippines
    Juinio, Marie Antoinette R.; Meñez, Lambert Anthony B.; Villanoy, Cesar L.; Gomez, Edgardo D. (Oxford University Press (OUP), 1989-11-01)
    Field surveys were conducted to determine distribution and abundance of giant dam resources in the Philippines. All seven known species of giant clams were recorded with Tridacna crocea, T. maxima and T. squamosa occurring the most frequently. The larger species T. derasa, T. gigas, Hippopus hippopus and H. porcellanus were relatively rare. The reduction of giant dam stocks in the Philippines is due to the uncontrolled exploitation of this resource which is primarily gathered for shellcraft and as supplementary diet in coastal villages.