Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 Oceanologia

Powiadomienia systemowe

Sesja wygasła!
Sesja wygasła!
Sesja wygasła!

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Noctiluca blooms intensify when northwesterly winds complement northeasterlies in the northern Arabian Sea: Possible implications

Sarma Nittala Subrahmanya, Baliarsingh Sanjiba Kumar, Pandi Sudarsana Rao, Lotliker Aneesh Anandrao, Samanta Alakes

Oceanologia

2022

No. 64 (4)

717--734

Wind systems are known as nutrient sources playing significant roles in the oceanic realm and global climate oscillations. This study explores, for the first time, the effect of winds on the winter blooms of the mixotrophic dinoflagellate, the green variant of Noctiluca scintillans (NSG) in the northern Arabian Sea. When the NSG abundance was lower (i.e., <∼10000 cells l−1), it was coupled to silicic acid (H4SiO4), on which diatoms (phytoplankton) in turn depended. At higher abundance (i.e., NSG>∼10000 cells l−1), H4SiO4 and H4SiO4:DIN (dissolved inorganic nitrogen) ratio fell. The NSG was then intensely green and chlorophyll-a richer, attributed to a change in the mode of NSG's nutrition from heterotrophy to autotrophy-dominance. The back-trajectory model revealed that the winds were mostly northeasterly (NE) initially (during February) and were north-westerly (NW) towards the end of winter (March). Separately for the NE and NW winds, the NSG abundance was 10655±18628 and 28896±46225 cells l−1, respectively. The H4SiO4:DIN ratio correspondingly reached <0.2 and ≥0.4. The NSG was modelled with high significance (p<0.001, N=33) versus the NE and NW wind speeds. Thus, while the NE winds deepened the mixed layer and caused nutrient enrichment and phytoplankton production, the NW winds facilitated the recovery of the H4SiO4:DIN ratio and economical use of H4SiO4 for phytoplankton production. It is hypothesized that this process is helped by iron input from NW desert winds during the latter part of winter when the NSG blooms intensify.

Satellite estimates of the long-term trend in phytoplankton size classes in the coastal waters of north-western Bay of Bengal

Miranda Joereen, Lotliker Aneesh Anandrao, Baliarsingh Sanjiba Kumar, Jena Amit Kumar, Samanta Alakes, Sahu Kali Charan, Kumar Tummala Srinivasa

Oceanologia

2021

No. 63 (1)

40--50

The study presents long-term variability in satellite retrieved phytoplankton size classes (PSC) at two coastal sites, off Gopalpur and Visakhapatnam, in the north-western Bay of Bengal. The abundance-based models by Brewin et al. (2010) (B10) and Sahay et al. (2017) (S17), for retrieval of PSC (micro, nano, and picophytoplankton), from satellite data, were validated. Both the models performed well in the retrieval of nano and microphytoplankton. However, B10 performed poorly in retrieving picophytoplankton. The statistical analysis indicated better performance of the S17 model and hence was applied to Moderate Resolution Imaging Spectroradiometer onboard Aqua satellite (MODISA) data to understand the temporal (at monthly climatology) and spatial variability (from nearshore to offshore). The spatial distribution indicated nearshore dominance of micro and offshore dominance of picophytoplankton. In nearshore waters off Gopalpur, microphytoplankton dominated throughout the year except for months of south-west monsoon (June and July) where the dominance of picophytoplankton was observed. All PSC exhibited similar distribution at an annual scale with a primary peak during pre-monsoon (March and April) and a secondary peak during post-monsoon (September-November). However, microphytoplankton concentration during post-monsoon was higher off Gopalpur in comparison to Visakhapatnam. The higher microphytoplankton concentration during pre-monsoon was attributed to recurrent phytoplankton blooms. Whereas, post-monsoon increment could be attributed to enhanced phytoplankton growth by availing nutrients sourced from monsoonal precipitation induced terrigenous influx. The outcome of the present study recommends the use of the S17 model for satellite retrieval of PSC from the north-western Bay of Bengal.