11. University of the Philippines - Marine Science Institute (UP - MSI)
Permanent URI for this communityhttps://repository.unesco.gov.ph/handle/123456789/10
University of the Philippines - Marine Science Institute (UP - MSI) - Philippines - contributions to address the Ocean Decade Challenges
Browse
2 results
Search Results
- Effect of starvation on development and survivorship of naupliar Calanus pacificus (Brodsky)Lopez, M. D. G. (Elsevier, 1996-10)In the marine planktonic copepod, Calanus pacificus (Brodsky), survivorship and development rate during the remaining naupliar stages were reduced when initial feeding was delayed for ~ 10 h after molting into naupliar stage III (NIII). In otherwise well-fed stages NIII-NVI, development and survivorship were reduced after starvation periods > 6 h and > 14 h, respectively. Molting rate and survivorship were lower in response to transient starvation than in response to constantly low food supplies. Stage NV was the least sensitive to transient starvation, while stages NIII and NVI were the most susceptible. Molting rates were reduced even after abundant food was subsequently provided. Thus, ambient food concentration at the time a population is sampled may not be an adequate index of future cohort success. Estimates of fine-scale to micro-scale particle distributions in situ suggest that NIII, the first feeding stage, is the instar most likely to experience short starvation periods if hatching occurs well below phytoplankton-rich strata.
- Feeding and diel vertical migration cycles of Metridia gerlachei (Giesbrecht) in coastal waters of the Antarctic PeninsulaLopez, M. D. G.; Huntley, M. E. (Springer, 1995-01)Diel vertical migration and feeding cycles of adult female Metridia gerlachei in the upper 290 m of a 335-m water column were measured during a total of 65 h in two periods of early summer (Dec 20–21 and Dec 25–26, 1991). Samples collected in eight depth strata by 35 MOCNESS tows (333-μm mesh) were analyzed for abundance and mean individual gut pigment content. Most of the copepod population was concentrated in a 50-m depth interval at all times. Feeding began simultaneously with nocturnal ascent from a depth of 200–250 m at ≈ 18:00 h (local time), when the relative change in ambient light intensity was greatest. Ingestion rate increased exponentially (ki = 0.988 h−1) at double the gut evacuation rate (ke = 0.488 h−1) as the population moved upward at 22.3–26.5 m h−1 through increasing concentrations of particulate chlorophyll-a. Although the bulk of the population did not move to depths shallower than 50 m, and began its downward migration at a rate of 20.8–31.7 mh−1 in complete darkness, individual females continued to make brief excursions into chlorophyll-rich surface waters (4–8 μg l−1) during the first few hours of population descent. Ingestion rate diminished abruptly by one order of magnitude (ki = 0.068 h−1) at dawn (≈ 03∶30 h). Within four more hours, the population had reached its daytime depth and gut pigment content remained constant at a minimum value until the next migration cycle. No feeding appeared to take place at depth during the day. Ingestion by M. gerlachei females removed < 4% of daily primary production, with only ≈ 20% of this amount being removed from surface waters by active vertical transport.