THE NITROGEN CYCLE IN SURFACE WATERS PHYTOPLANKTON ELEMENTAL

THE NITROGEN CYCLE IN SURFACE WATERS

PHYTOPLANKTON ELEMENTAL COMPOSITION • • • O C K H N Ca S Na P 53% 27% 6. 2% 5. 5% 4. 6% 1. 0% 0. 7% 0. 5% • • • Fe Mg Zn Cu B Mn Co V Mo 0. 4% 0. 3% 0. 02% 0. 01% 0. 009% 0. 0006% 0. 0001% • Si 0. 1%; DIATOMS 20%

N 2

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 p 233) p. H NH 4+ : NH 4 OH 6 3000: 1 7 300: 1 8 30: 1 9. 5 1: 1

NITROGEN CYCLE

NITRIFICATION • NH 4+ NO 2 - Nitrosomonas – Requires O 2; wide range of temperature and p. H • NO 2 - NO 3 - Nitrobacter – Requires O 2; warm temperatures and low p. H

DENITRIFICATION • C 6 H 12 O 6 + 12 NO 3 • C 6 H 12 O 6 + 8 NO 2 - 12 NO 2 - + 6 CO 2 +6 H 2 O 4 N 2 + 2 CO 2 + 4 CO 3 -- + 6 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