National Committee on Marine Sciences (NCMS)
Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/6
Browse
4 results
Search Results
- Utility of low-cost recreational-grade echosounders in imaging and characterizing bubbly coastal submarine groundwater dischargeGabuyo, Mary Rose P.; Siringan, Fernando P. (Elsevier, 2022-01)Despite the growing knowledge on the significance of submarine groundwater discharge (SGD), mapping its occurrence is a continuing challenge. This study explores the capability and applicability of low-cost, off-the-shelf, recreational-grade echosounders (RGESs) to image different types and locate point sources of bubbly coastal SGD. Standard and systematic methodologies for efficient imaging and processing were established. The use of RGES was validated using a research-grade side scan sonar (RGSSS), continuous resistivity profiling, conductivity-temperature-depth casting, and MantaCam and SCUBA diving surveys. Lower frequencies (77/83 kHz) of RGESs showed more distinct acoustic signatures of bubbly SGD, as these were nearly the same as the effective resonance frequency of the bubbles. The clusters of bubbly discharges have higher backscatter strength than the water column noise, resulting in the definitive and convenient manual detection of SGD features. Hence, showing more accurate point sources of SGD. Three types of known SGD occurrence were identified and characterized based on acoustic behavior and spatial distribution: 1) sparse, discrete and sporadic discharge over wide area, 2) curtain, high and continuous bubble concentrations from widespread discharge, and 3) spring, direct bubble discharge from intense seafloor degassing at a single point source. These results showed that RGES provides a good alternative for more efficient and cost-effective preliminary coastal SGD works. Additional research on areas with water-dominated discharge but no bubbling is recommended.
- Growth, nitrate uptake kinetics, and biofiltration potential of eucheumatoids with different thallus morphologiesNarvarte, Bienson Ceasar V.; Genovia, Tom Gerald T.; Hinaloc, Lourie Ann R.; Roleda, Michael Y. (Wiley, 2021-12-30)The declining production of commercially important eucheumatoids related to serious problems like increasing susceptibility to ice‐ice disease and epiphytism may be ameliorated by nutrition. This ushered to an increasing interest in incorporating seaweeds into an integrated multi‐trophic aquaculture (IMTA) setup to take up excess inorganic nutrients produced by fish farms for their nourishment. In this regard, it is important to understand the nutrient uptake capacity of candidate seaweeds for incorporation in an IMTA system. Here, we examined the growth, nitrate (NO3‐) uptake kinetics and biofiltration potential of Eucheuma denticulatum and three strains of Kappaphycus alvarezii (G‐O2, TR‐C16 and SW‐13) with distinct thallus morphologies. The NO3‐ uptake rates of the samples were determined under a range of NO3‐ concentration (1‐ 48 µM) and uptake rates were fitted to the Michaelis‐Menten saturation equation. Among the examined eucheumatoids, only SW‐13 had a linear response to NO3‐ concentration while other strains had uptake rates that followed the Michaelis‐Menten saturation equation. Eucheuma denticulatum had the lowest Km (9.78 ± 1.48 µM) while G‐O2 had the highest Vmax (307 ± 79.3 µmol · g‐1 · min‐1). The efficiency in NO3‐ uptake (highest Vmax/Km and α) was translated into the highest growth rate (3.41± 0.58 % · d‐1) measured in E. denticulatum. Our study provided evidence that eucheumatoids could potentially take up large amount of NO3‐ and fix CO2 when cultivated proximate to a fish farm as one component of an IMTA system. During a 45‐d cultivation period of eucheumatoids, as much as 370 g NO3‐ can be sequestered by every 1 kg initial biomass E. denticulatum growing at 3% · d‐1. Furthermore, based on our unpublished photosynthetic measurements, the congeneric K. striatus can fix 27.5 g C · kg‐1 DW during a 12‐h daylight period.
- Water quality bioassays in two Bermudan harbours using the ciliate Euplotes vannus, in relation to tributyltin distributionSlabbing, A. R. D.; Soria, S.; Burt, G. R.; Cleary, J. J. (Elsevier, 1990-01)Laboratory cultures of the ciliate Euplotes vannus were used to bioassay water samples taken from the sea surface, 0.5 m and near bottom at stations along contamination gradients in Castle Harbour and Hamilton Harbour on Bermuda. Inhibition of population growth rate was used as an index of exposure to toxic contaminants. Significant differences in growth rates from near-bottom water samples taken at two stations in Castle Harbour were reflected in differing sediment concentrations of metals and petroleum hydrocarbons. Bioassays of four Hamilton Harbour samples indicated significant differences between control and contaminated sites when results from all three depths were pooled. Highest concentrations of tributyltin (⩽ 307 ng TBT·1−1) occurred in the surface microlayer, though measurements varied widely on the two sampling occasions. At 0.5 m, concentrations were much less variable and showed a steady decline from the head of Hamilton Harbour (41 ng TBT· 1−1) seawards to the control site (0.9 ng TBT · 1−1). While these concentrations are high enough to be toxic to some species, it is known from experimental work that TBT alone could not have accounted for the depression of ciliate growth rates in these bioassays.
- Phosphorus as a driver of nitrogen limitation and sustained eutrophic conditions in Bolinao and Anda, Philippines, a mariculture-impacted tropical coastal areaFerrera, Charissa M.; Watanabe, Atsushi; Miyajima, Toshihiro; San Diego-McGlone, Maria Lourdes; Morimoto, Naoko; Umezawa, Yu; Herrera, Eugene; Tsuchiya, Takumi; Yoshikai, Masaya; Nadaoka, Kazuo (Elsevier, 2016)The dynamics of nitrogen (N) and phosphorus (P) was studied in mariculture areas around Bolinao and Anda, Philippines to examine its possible link to recurring algal blooms, hypoxia and fish kills. They occur despite regulation on number of fish farm structures in Bolinao to improve water quality after 2002, following a massive fish kill in the area. Based on spatiotemporal surveys, coastal waters remained eutrophic a decade after imposing regulation, primarily due to decomposition of uneaten and undigested feeds, and fish excretions. Relative to Redfield ratio (16), these materials are enriched in P, resulting in low N/P ratios (~ 6.6) of regenerated nutrients. Dissolved inorganic P (DIP) in the water reached 4 μM during the dry season, likely exacerbated by increase in fish farm structures in Anda. DIP enrichment created an N-limited condition that is highly susceptible to sporadic algal blooms whenever N is supplied from freshwater during the wet season.