Chlorophylls and their Degradation in Nature - Photobiogeochemistry of Organic Matter - page 735

6.1 Possible Mechanisms For the Management
of Eutrophication by Control of Primary Production

Most present studies try to correlate Chl a with nutrients, in order to regulate
Chl a , primary production or photosynthesis by controlling nutrients or by
other measures of flood disturbance frequency or of days available for accrual
(Biggs 1985 , 1995 , 2000 ; Biggs et al. 1998 , 1999 ; Lohman et al. 1992 ; Welch
and Lindell 1992 ; Chapra 1997 ; Dodds et al. 1998 ; Chetelat et al. 1999 ; Huszar
et al. 2006 ). Nutrients, particularly NO 3 and PO 4 3 − are produced mostly by

DOM and POM (e.g. phytoplankton species or algae or cyanobacteria), via
photoinduced or microbial respiration and degradation. This issue strongly sug-
gests that regulating Chl a is vital for the control of DOM and POM in aquatic
environments. DOM and POM are in fact the sources of all reactants such as
CO 2 , DIC, H 2 O 2 , nutrients and autochthonous DOM, which are responsible for
photosynthesis and, therefore, for the primary production of Chl a (see chap-
ters “ Photosynthesis in Nature: A New Look ” and “ Impacts of Global Warming
on Biogeochemical Cycles in Natural Waters ” ). DOM and POM along with
global warming can lead to excess primary production and to photosynthesis,
as shown in chapter “ Impacts of Global Warming on Biogeochemical Cycles
in Natural Waters ” . A conceptual model of primary production enhancement
and three important steps for remediation, to control algal blooms are exten-
sively discussed in Sects. 5 and 5.1 of chapter “ Impacts of Global Warming on
Biogeochemical Cycles in Natural Waters ” . The same measures can be adopted
to control photosynthesis and, therefore, to limit primary production or Chl a
concentration. This activity can reduce eutrophication in natural waters.

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7 Scope of the Future Research

DOM along with POM (e.g., algae or phytoplankton) can play an important role
in the formation of SCM and DCM. The mechanism behind SCM and DCM for-
mation may pave the way for future research. Formation of H 2 O 2 in DCM layer
by phytoplankton might be important, and distribution of H 2 O 2 as well as its for-
mation from the existing phytoplankton in DCM could be interesting to understand
the mechanism of DCM formation. Almost all of previous studies dealt with nutri-
ents (total nitrogen, NO 3 , and total phosphate or PO 4 3 − ), but they have

some problems. First, DOM and POM can release nutrients in natural waters by
photoinduced or microbial respiration or degradation. Therefore, release and uptake
of nutrients during photosynthesis has limited importance in waters with high con-
tents of DOM and POM or high contents of nutrients. Second, waters with high
contents of DOM and POM can produce DIC, CO 2 , H 2 O 2 and so on, which are
directly linked to photosynthesis and, therefore, to primary production (see chapter
“ Photosynthesis in Nature: A New Look ”). Therefore, DOM and POM should be
more directly linked to Chl a than nutrients are. Important research needs can thus

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or NH 4