THE NITROGEN CYCLE IN SURFACE WATERS
PHYTOPLANKTON ELEMENTAL COMPOSITION O53% C27% K6.2% H5.5% N4.6% Ca1.0% S0.7% Na0.7% P0.5% Fe0.4% Mg0.4% Zn0.3% Cu0.02% B0.01% Mn0.009% Co0.0006% V0.0006% Mo0.0001% Si0.1%; DIATOMS 20%
N2N2
FIGURE 12-1; N 2 IN GREEN LAKE AND BELOIE LAKE
N-FIXATION
CYANOBACTERIA AND N-FIXATION
OTHER MICROBIAL NITROGEN FIXERS Azotobacter
MEROMICTIC LAKES AND N-FIXATION
SYMBIOSIS N-FIXATION OFTEN THROUGH SYMBIOSIS WITH VASCULAR PLANTS e.g. – Alders (wetland plants) – Legumes – Azolla (aquatic fern)
AMMONIUM AND NITRATE
AMMONIUM BY-PRODUCT OF DEAMINATION NH 4 + and NH 4 OH (see p233) pHNH 4 + : NH 4 OH 63000:1 7300:1 830:1 9.51:1
NITROGEN CYCLE
NITRIFICATION NH 4 + NO 2 - Nitrosomonas – Requires O 2 ; wide range of temperature and pH NO 2 - NO 3 - Nitrobacter – Requires O 2 ; warm temperatures and low pH
DENITRIFICATION C 6 H 12 O NO NO CO 2 +6H 2 O C 6 H 12 O 6 + 8NO 2 - 4N 2 + 2CO 2 + 4CO H 2 O
REDUCTION IN AN ANOXIC ENVIRONMENT
NITRIFICATION AND DENITRIFICATION
ORGANIC NITROGEN DISSOLVED ORGANIC NITROGEN (DON) PARTICULATE ORGANIC NITROGEN (PON) DON:PON INCREASES WITH EUTROPHICATION
NITRATE AND PON
INORGANIC NITROGEN IN WINTERGREEN LAKE
NITROGEN CYCLE
NITROGEN IN STREAMS
NUTRIENT SPIRALLING
NITROGEN LOADING
NITRATE IN THE CHESAPEAKE BAY
Dead Zone summer 2011, USEPA