T H E PRODUCTION O F M A R I N E I'LANKTON
141
But some may arise from the excretion of planktonic organisms;
Pomeroy et al. (1963) have called attention t o the importance of excreted phosphorus in production. Organic nitrogen (urea, amino-acids,
etc.) typically forms a fraction of the excr1:ted nitrogen of marine
animals. But organic material is also liberated during the metabolism
of phytoplankton algae, though Duursma (1!361) contends that practically all the dissolved organic matter in sea water is derived from
decomposition and no clear evidence exists for appreciable quantities
being liberated. Apart from highly toxic materials liberated in the
growth of species like Gymnodinium, Goniaulax, Prymnesium (cf.
Gunter et al., 1948; Abbott and Ballantine, 19b7; Brongersma - Sanders
1957) which can affect adversely a wide range of animals, there are a
number of algae which can favour or discourage the growth of other
species by excreting growth-promoting or growth-inhibiting substances
(cf. Jerrgensen and Steemann Nielsen, 1961). There are a number of
investigations reporting the production of ext ra-cellular substances by
marine algae. Collier (1953) described carbohydrate-like substances,
apparently produced by algae, and later (1958) showed the production
of carbohydrate-like substances by Prorocentrum and by Gymnodinium
breve. Guillard and Wangersky (1 958) demonstrated the production of
soluble extra-cellular ca,rbohydrates by a variety of flagellates, the
amount released being highest in stationary c r declining cultures. Curl
and McLeod (1961), studying the culture of Skeletonema, suggested that
extra-cellular substances are produced a t certain stages of growth.
Parallel work with fresh water algae such as that of Fogg and of
Proctor (1957) indicates that nitrogenous cirganic materials, carbohydrate-like substances and lipids produced by algae may be liberated
into the water. Many workers have suggested chat the secretion of these
substances tends to occur when algae are becoming somewhat unhealthy, especially during intensive blooms. While there is considerable
evidence that this is true for many specie,3, Fogg (1963) advances
strong arguments for the view that some excretion of material occurs
during normal healthy growth of both fresh .water and marine algae.
Indeed, Fogg criticizes the 14C method for estimating primary production by suggesting that an appreciable propclrtion of the fixed carbon
may appear in soluble form in the filtrate, quite apart from losses from
the breakage of cells during filtration. The recent experiments of Antia
et al. (1963), using the plastic sphere technique, have confirmed a considerable excretion of organic matter by healthy algae. Fogg draws
particular attention to the importance of glycollic acid in algal metabolism; his experiments suggest that quite an appreciable amount may
be released during active photosynthesis of phytoplankton. Though this
may introduce errors in calculating the primary production, it should
141
But some may arise from the excretion of planktonic organisms;
Pomeroy et al. (1963) have called attention t o the importance of excreted phosphorus in production. Organic nitrogen (urea, amino-acids,
etc.) typically forms a fraction of the excr1:ted nitrogen of marine
animals. But organic material is also liberated during the metabolism
of phytoplankton algae, though Duursma (1!361) contends that practically all the dissolved organic matter in sea water is derived from
decomposition and no clear evidence exists for appreciable quantities
being liberated. Apart from highly toxic materials liberated in the
growth of species like Gymnodinium, Goniaulax, Prymnesium (cf.
Gunter et al., 1948; Abbott and Ballantine, 19b7; Brongersma - Sanders
1957) which can affect adversely a wide range of animals, there are a
number of algae which can favour or discourage the growth of other
species by excreting growth-promoting or growth-inhibiting substances
(cf. Jerrgensen and Steemann Nielsen, 1961). There are a number of
investigations reporting the production of ext ra-cellular substances by
marine algae. Collier (1953) described carbohydrate-like substances,
apparently produced by algae, and later (1958) showed the production
of carbohydrate-like substances by Prorocentrum and by Gymnodinium
breve. Guillard and Wangersky (1 958) demonstrated the production of
soluble extra-cellular ca,rbohydrates by a variety of flagellates, the
amount released being highest in stationary c r declining cultures. Curl
and McLeod (1961), studying the culture of Skeletonema, suggested that
extra-cellular substances are produced a t certain stages of growth.
Parallel work with fresh water algae such as that of Fogg and of
Proctor (1957) indicates that nitrogenous cirganic materials, carbohydrate-like substances and lipids produced by algae may be liberated
into the water. Many workers have suggested chat the secretion of these
substances tends to occur when algae are becoming somewhat unhealthy, especially during intensive blooms. While there is considerable
evidence that this is true for many specie,3, Fogg (1963) advances
strong arguments for the view that some excretion of material occurs
during normal healthy growth of both fresh .water and marine algae.
Indeed, Fogg criticizes the 14C method for estimating primary production by suggesting that an appreciable propclrtion of the fixed carbon
may appear in soluble form in the filtrate, quite apart from losses from
the breakage of cells during filtration. The recent experiments of Antia
et al. (1963), using the plastic sphere technique, have confirmed a considerable excretion of organic matter by healthy algae. Fogg draws
particular attention to the importance of glycollic acid in algal metabolism; his experiments suggest that quite an appreciable amount may
be released during active photosynthesis of phytoplankton. Though this
may introduce errors in calculating the primary production, it should