PROGRESS SERIES Prog. Ser. a shallow - PDF document

PROGRESS SERIES Prog. Ser. a shallow Ecol. Prog. greater than saturating when the summed production duration involving samples taken a day compared with produc- a single incubation representing the time interval al., 1973; the present study we involving time-course a shallow in Vineyard Massachusetts, midway monthly intervals mo period to assess ature upon the measurement production measurements 6 study days between 29, 1981 a series approximately 3 h intervals was collected 1 m with a 6 Niskin bottle, Institution (WHOI) the balance incubation system, 1 1 vessels, in other Vineyard Sound studies was held at mixed continuously Two additional day starting other exposed a variable light (incident irradiation alter- nated in on the remaining dates. The the day during the were measured study site with was recorded on an Eppley pyroheliometer where the performed time-course specific activity 80 to 100 by subsampling at about 15 min intervals the incubation. The samples ing enough 18 to 1.3. then sparged min to another scintillation scintillation counting on a conditions and Sound. Massachusetts, based full-day single end-point light levels duration surface surface 10 60% I, 30% I, (W h m-') May 14 10.5 14.5 6426 S-PC-S N.M." 1.4 N. M. June 11 17.0 16.0 7716 %lC 3.2 9.4 (9.1)' Jul 16 22.0 15.0 8018 S 1.3 (1.7)++ 3.8 N. M. Aug 5 23.0 11.0 3091 13.9 13.2 11.5 OC-R Sep 29 17.0 12 0 5031 OC-S 1.7 4.3 6.4 Oct 29 12.5 10.5 1057 0 C 5.7 7.3 6.7 S - full sun, PC - partly cloudy, intermittent clouds, effect on primary production phytoplankton species present in Vineyard pre-dawn sampling mo study 29, 1981 Count (cells Cylindrotheca closterium 3 42 2 6 2 1 other diatoms unident. naked other dinoflagellates Chroomonas arnphioxeia 4 8 21 137 2 1 Assorted other cryptornonads daily primary production by full day, single end-point (TP), by h rates back incubation extrapolated over full daily production Incremental daily production ratio ratio 0-3h 3-6h 6-9h 9-12h 14 22.2 33.6 1.5 1.8 3 1 128.4 19 (19) 117.2 145.5 another and the similarity between the was one September studies, however, during each than coincidental, thereby providing us with was observed were virtually (Fig. 6 days marked very low total each experiment was incubations was maximal and C). On sunny days, however, those incubation to full C) and the mid-day suppression in productivity (which common to was less the light was reduced to 30 on a sunny day when the last incubation day was uptake under these to occur light attenuation (down to 30 the time the entire Alternating the light about the same effect on uptake as represents incubation under Same as July 16, represents alternating light between represents incubation effect on incubation during with estimates methods, indicating Vineyard Sound stant light reduced to 60 constantly at sunlight (Fig. Primary productivity estimated primary productivity First, total daily production based observed that rates a given were sustained only slightly and September 5 and sunlight had effect on There was discernable seasonal temperature was when water temperatures were W h The general Our sampling station Vineyard Sound a shallow region vertical mixing throughout the year, thermograms compiled Our inability observe thermal location over (unpubl.) in conjunction with another study (Glibert this conclusion. irradiation always was attenuated at vertical mixing velocities, it assume that the resident phytoplankton populations never photoadapted particular light summarized in is a well-established, Often little between the various processes decrease in supersaturating light visible photochemical photooxidation); thus in most Ecol. Prog. 169-180, 1984 finally is is repairable Diatoms, in contrast, exhibit photochemical decay relatively lower so that rapid possible once times either or by cloud cover. in the pigment structure cryptomonads (Goodwin, primary production which water-column in a shallow environment such Vineyard Sound bottle incubations is not unexpected nature sonal response in those seasonal changes There seems little doubt, however, that incubations, serious surface productivity would all but summer experiments. these underestimates have had integrated water column productivity difficult to several light a clear the water be ca. study (Table high as do point out, however, that euphotic zone, reductions in productivity result a bottle incubation. well documented in in other studies suppression' in primary production observed was, To illustrate consider that had full-day incubation been employed have drawn the mistaken total daily production had 3 h the day raising the total daily production, reduced those early morning but, as 3 h incubations Table 6. primary productivity estimates based day, single end-point Water body Date Total TP Integrated May 1956 30 May 1956 Lake Werowrap, 2 Aug 1970 1976 12.0 Integrated values TP over entire water