Some development patterns of plankton communities in the upwelling areas of the Pacific Ocean

An intensive study of pelagc primary production and microplankton community respiration was carried out during an entire upwehng season in the Ria de Vigo (NW Spain). From April to November measurements of oxygen production and respiration using the hght-dark bottle technique were made twice a week at the surface. l % Light depth ( l % LD, 12 r 4 m) and 40 m (8 m above sea floor) alongside routine physical, chemical and biological measurements. During the major part of the survey period intermittent intrusions of cold, nutrient-rich upwelled water were observed In the ria with a periodicity of about 2 wk. Rates of gross primary production (GPP) were high but variable averaging 37.3 + 30.7 pM O2 d-' and 3.6 + 4.8 pM O2 d-' at the surface and l % LD respectively over the period of survey (n = 50). Rates of dark community respiration (DCR) were also high and variable with maximum values being observed in the surface layer where the seasonal average was 12.2 * 9.8 pM O2 d-l. At the l % LD and 40 m, DCR averaged 5.3 + 4.4 and 2.8 * 3.0 I.IM O2 d-l respectively. Although seasonal average and maximal DCR (up to 46.5 pM 0, d-l) were among the highest reported for coastal areas, microplankton production over the period of survey was dominated by autotrophic processes. Respiration losses by the microplankton community in the euphotic zone represented on average 43 % of estimated mean seasonal water column GPP (2.1 to 2.7 g C m-' d-l). Net heterotrophy in the aphotic layer consumed the equivalent of a further 25% of estimated water column GPP. The degree of coup h g between primary production and respiration was primarily controlled by upwelling. Dunng upwelling events respiration was generally low in the water column but it increased as a linear function of chlorophyll a concentrat~on (R2 = 0.55. n = 13) and GPP (R2 = 0.47, n = 13) in the surface layer. Under such condition phytoplankton appears as the dominant component of community respiration consuming 14 % of GPP. During penods of upwelling relaxation respiration was high relative to GPP High water column respiration rates extending occasionally down to 40 m took place at the expense of organic matter trapped inside the bay. The seasonal breakdown of thermal stratification in autumn presented a relationship between surface respiration and chlorophyll a or GPP similar to that observed during upwelling events. The large excess primary production during this period was not remineralised inside the ria, suggesting that a large fraction may be exported towards the shelf.

Section: Discussionsupporting

confidence: 90%

Seasonal and short-time-scale dynamics of microplankton community production and respiration in an inshore upwelling system

Moncoiffé¹,

Álvarez-Salgado²,

Figueiras³

et al. 2000

“…In our study, the phasing of GCP and DCR cons~sted of periods of positive production relaxing into negative production, a temporal succession similar to the longitudinal (i.e. time-dependent) succession reported for the Peruvian upwelling zone (Vinogradov & Shushkina 1978). Simple calculations of volume-based rates of NCP are misleading because of the difference in the depth distribution of GCP and NCP in mixed water.…”

Section: Spring Bloom Patternsupporting

confidence: 51%

Phasing of autotrophic and heterotrophic plankton metabolism in a temperate coastal ecosystem

Blight¹,

Bentley²,

Lefèvre³

et al. 1995

103

Plankton abundances, bacterial production, and the size distribution of oxygen rnetabolism and chlorophyll a concentration were determined through 3 seasonal cycles in the Menai Strait [North Wales, UK). Spring blooms were comprised of a diatom to Phaeocystis succession. Meso-and microphytoplankton dominated phytoplankton production and biomass during diatom blooms, and nanophytoplankton predominated during summer, when activity and biomass were low. Correlation analysis showed temperature to be the best predictor for chlorophyll a-specific gross colnmunity production. Bacterioplankton were implied to be the major resplrers Consequently the phasing of respiration in relation to photosynthesis was strongly influenced by bacterloplankton metabolism and abundance changes. The respiration maximum occurred 1 to 2 wk after the Phaeocystis abundance maximum. An explanation for this temporal lag was sought by considering the time scales of flow of organic material between the phytoplankton and the bacter~oplankton. The observations were consistent with routes via a slo\vly cycling pool, such as polymeric organic material. This pool would function as a reservoir and result in microheterotrophic respiration persisting after the decline of photosynthesis, and causing a positive to negative temporal sequence in net community production.

“…Our analysis of the state of epipelagic plankton communities in various regions of the Pacific Ocean, in part described earlier (Vinogradov et al, 1976Vinogradov and Shushkina, 1978;Shushkina et al, 1978Shushkina et al, , 1980, as well as numerous data from the literature, permit us to define 5 successional stages in the development of epipelagic plankton communities (Table 1):…”

Section: Stages O F Development Of Plankton Communitiesmentioning

confidence: 94%

Succession of marine epipelagic communities

Vinogradov¹,

Shushkina²

1984

The changes occurring in the structural-functional characteristics of plankton communities (assemblages) in the course of their development have been repeatedly described and modelled for various oceanic regions. However, the tracing of a particular con~munity through the whole course of its successional development is practically unattainable and the comparison of the serial stages in different communities reflects neither the duration of each separate stage nor their strict sequence. We propose here a method of ranging of the communities observed according to the value of Q = Ig D/P, (maturity index); this makes it possible to follow changes in the community's characteristics in the course of its quantitatively assessed development. The scale comprises designated intervals corresponding to different community-development stages and their coincidence with the trophicity gradations of the waters that these communities inhab~t. The influence of frontal zones on the development of plankton communit~es is discussed and a comparison is given of the quantitative charactenstics of communities at different stages of development in the eastern tropical Paciflc Ocean and in the Black Sea.