Chlorophyll a was not measured before 2008.
Algal Cover was not measured before 2009.
Temperature is a measured physical property of water indicating
how hot or cold it is, which can affect its chemical or physical properties. Water temperature can also
affect the distribution of aquatic organisms.
Salinity is the measured quantity of dissolved salt present in
water. Salinity levels, usually measured in parts per million (ppm), can influence the distribution of
living organisms.
Conductivity is the water's ability to conduct an electrical
current, indicating the quantity of inorganic salts or chemicals present in water.
Ammonia or NH
4 is an essential nutrient for plant growth
and can be a limiting reagent in estuaries. Increased ammonia concentrations can lead to
eutrophic
conditions.
Phosphate is a required nutrient for plant growth and is generally
found in lower concentrations than nitrate in Elkhorn Slough. Elevated concentrations will still
contribute to overall
eutrophication.
Nitrate is a vital nutrient for plants. Elevated concentrations of
nitrate can contribute to
eutrophic
conditions in the estuary by enabling algae and phytoplankton to grow excessively.
This is a calculated concentration based on the measured Ammonia
concentration, pH, and temperature. Free ammonia can be very toxic to fish if the concentration rises
above 0.025 mg/L.
Turbidity is a measure of the clarity of the water. The higher the
turbidity the less clear the water is. Water clarity effects the ability for sub-aquatic vegetation to
grow, mainly eelgrass in Elkhorn Slough. Eelgrass and other aquatic vegetation not only provide habitat
for fish and other species but add oxygen to the water as well as reduce water movement allowing for
sediment to settle out of the water column, increasing water clarity.
Dissolved oxygen (DO) is vital for the survival of aquatic organisms. Two
thresholds are defined for dissolved oxygen because a lack of oxygen will cause animals to suffocate while
excess oxygen is an indication of excess growth or
eutrophication.
A measure of pH indicates how acidic or basic the water is at the sample
site. A pH of 7 is neutral. A pH below 7 is acidic and the acidity threatens organisms that have any type
of calcium carbonate body parts which can be dissolved. A pH above 7 indicates basic conditions and can
effect reactive molecules in the water, such as Ammonium, which tend to form free ammonia, a toxin to
fish.
Chlorophyll is molecule which allows all plants, including microscopic
algae called phytoplankton, to photosynthesize. An indication of
eutrophication
in an estuary is excessive population growth of phytoplankton and so chlorophyll is used as a biological
indicator of eutrophication in a system. Eutrophication is caused by excessive nutrients coming into a
system promoting plant growth. This can lead to increased turbidity, decreased light penetration and
decreased sub-aquatic vegetation. It can also lead to excessive dissolved oxygen during the day and the
depletion of oxygen to anoxic conditions during the night.
Algal cover is also a biological indicator of
eutrophication
in a system. Excess nutrients in an estuarine system promote excess algal growth which creates floating
mats. These floating mats block vital light to the
benthos.
Any organisms present on the bottom during the high tide are smothered as the tide recedes, reducing these
organisms ability to grow and survive.
