Itociprocally, ciwtton tlioxi(lc ooiicrntriit’ion tends to increase a t
night itiid tleorciise during the diby : for technical convenience, these
changes iiro computd from 1) ti mtwnir(~ment,s to which they are invcrsuly corrchtcd (t8hiis oxygen iiiitl p€l rurveR m e nearly parallel). In
sonw highly productive Texas bays, niax/trtin ratios for total COz ranged
from 1*03:1.00 to 1.38:1*00 ( h r k o/ al., 1958; ratios calculated here
from their Fig. ti 13); pH in a diiitom bloom increased steibdily from
8.5 in t,he morning to 9.5 in the afternoon (Ityther ~t d., 1958); less
rogular chnngcs were rioted in iL p t c h rcwf environment (Jones, 1963).
Siirprisingly, such vnrititions rue seldom if ever taken into iiccotint in
1 4 C prodiictivity ~ ~ ~ ~ i ~ s u r ~ i n e n t s
: they might be ricgligible in oligotrophic
tireas, for which no informittion is available. As in the case of oxygen,
COz chnnges can be used for estiniiiting primary production whenever
the Ii~ttcr is high enoiigh (Verduin, 1956, 1957; Park et nl., 1968;
Reyers, 1964).
Changes in (YOz content resulting from respiration and photosynthesis will in turn induce it change in the electrical conductance of
sea wtiter, which xuggests another approach and a new tool in productivity studies (Park and Curl, 1965; Park et al., 1960).
D. Macro- and micronutrients
I)id changes in inorganic nitrogen and phosphorus concentrations
are reviewed above in connection with nritrient, iiptake. The question
ihrises whether or to which extent- thr availtibility of nutrient9 decremes im the d ; ~ y proceeds, utitIil i i deficiency or even exhaustion is
laiichecl in the ;ift,ernoon,
cotitcmpliLti’(f by Vollenweider and Nauwerck (1!)81) o r Vollenweider ( 1!)65) : i f so, nocturnal excretion and
regeneriition, involving bacteria i d zoopliinkton in addition to phytopliinkton, would complete the cycle. The answer probably depends on
tho niitrirnt under considertition (it is kenerally ;accepted that, turnover
is faster for E’ than for N), o i l tiixonomic cornpoRition and qjecific
grovrth kiiietics (rf. Rppley et d., 1971 and klulone, 1971), on the stibgc
of succession and on the incidence of other limiting factors. StrosH
et al. ( I 973) have recently proposed two alternative models for the
Michi~eli~-Menten kinetics according to (1) the “ forcing hypothesis ” :
photosynthetic capacity as a fii nction of nutrient availability, (2) the
“ phasing hypothesis ” : photosynthetic capacity as 8 function of an
intrinsic time-dependent organization.
Miiller-Hneckel (1966) offers clear evidence of a die1 periodicity in
silica coiitant in the waters of a saline creek: concentrations are the
highest a t dawii and then decrease until the evening, presumablr
reflecting siliciuin uptake by diat>oms after cell division. Furthermore,
night itiid tleorciise during the diby : for technical convenience, these
changes iiro computd from 1) ti mtwnir(~ment,s to which they are invcrsuly corrchtcd (t8hiis oxygen iiiitl p€l rurveR m e nearly parallel). In
sonw highly productive Texas bays, niax/trtin ratios for total COz ranged
from 1*03:1.00 to 1.38:1*00 ( h r k o/ al., 1958; ratios calculated here
from their Fig. ti 13); pH in a diiitom bloom increased steibdily from
8.5 in t,he morning to 9.5 in the afternoon (Ityther ~t d., 1958); less
rogular chnngcs were rioted in iL p t c h rcwf environment (Jones, 1963).
Siirprisingly, such vnrititions rue seldom if ever taken into iiccotint in
1 4 C prodiictivity ~ ~ ~ ~ i ~ s u r ~ i n e n t s
: they might be ricgligible in oligotrophic
tireas, for which no informittion is available. As in the case of oxygen,
COz chnnges can be used for estiniiiting primary production whenever
the Ii~ttcr is high enoiigh (Verduin, 1956, 1957; Park et nl., 1968;
Reyers, 1964).
Changes in (YOz content resulting from respiration and photosynthesis will in turn induce it change in the electrical conductance of
sea wtiter, which xuggests another approach and a new tool in productivity studies (Park and Curl, 1965; Park et al., 1960).
D. Macro- and micronutrients
I)id changes in inorganic nitrogen and phosphorus concentrations
are reviewed above in connection with nritrient, iiptake. The question
ihrises whether or to which extent- thr availtibility of nutrient9 decremes im the d ; ~ y proceeds, utitIil i i deficiency or even exhaustion is
laiichecl in the ;ift,ernoon,
cotitcmpliLti’(f by Vollenweider and Nauwerck (1!)81) o r Vollenweider ( 1!)65) : i f so, nocturnal excretion and
regeneriition, involving bacteria i d zoopliinkton in addition to phytopliinkton, would complete the cycle. The answer probably depends on
tho niitrirnt under considertition (it is kenerally ;accepted that, turnover
is faster for E’ than for N), o i l tiixonomic cornpoRition and qjecific
grovrth kiiietics (rf. Rppley et d., 1971 and klulone, 1971), on the stibgc
of succession and on the incidence of other limiting factors. StrosH
et al. ( I 973) have recently proposed two alternative models for the
Michi~eli~-Menten kinetics according to (1) the “ forcing hypothesis ” :
photosynthetic capacity as a fii nction of nutrient availability, (2) the
“ phasing hypothesis ” : photosynthetic capacity as 8 function of an
intrinsic time-dependent organization.
Miiller-Hneckel (1966) offers clear evidence of a die1 periodicity in
silica coiitant in the waters of a saline creek: concentrations are the
highest a t dawii and then decrease until the evening, presumablr
reflecting siliciuin uptake by diat>oms after cell division. Furthermore,