Data
Integration and Interpretation
Please read about the advanced floating lab before working
on this section. Below is a summary of
local productivity and
other conditions that affect our coastline.
Use these descriptions as a reference or guide to interpret data
acquired during the advanced floating lab or for the web-lab. Take your time and have some fun with this.
1) Normal Southern California Winter
The
productivity on the Southern California coast is controlled by coastal
winds and the thermocline. In the winter, there is a weak thermocline
and coastal winds are from the northwest.
Both conditions are ideal for the upwelling
of nutrients that can be present on a healthy
seabed. A healthy seabed is generally brown or greenish in color, has a
rich earthy/ocean smell and has a significant number of decomposers. The water sweeps across the healthy seabed
and picks up nutrients, these nutrients are then pushed into the photic zone
where the phytoplankton use the nutrients and sunlight to reproduce. Nutrients
can also be added from land-based runoff. This is usually more local in extent
and is considered to be secondary to upwelling for the supply of nutrients. The
water in highly productive areas can be greenish in color and not very clear
due to the abundant phytoplankton. Dissolved oxygen levels can be higher in
productive areas within the photic zone due to phytoplankton expelling
oxygen. Most
all fish species caught are in their proper
range. Here’s a
summary of our normal winter conditions.
2) Normal Southern California Summer
In the
summer, we have a strong thermocline and the coastal winds come from the
southwest. This creates conditions that
are ideal for downwelling. The surface water is
super-heated offshore and pushed onshore and down. This provides oxygen to the seabed and enhances nutrient
production. The water is blue in color
and very clear. Phytoplankton productivity is low. There may be lower dissolved oxygen
(normal range) than winter b/c of warmer water and less phytoplankton. Most all fish
species caught are in their proper range. Here’s a summary of our normal summer conditions
3)
El Nino years
During El Nino years, a strong
thermocline develops and exists all year around so upwelling of nutrients to the
photic zone does not occur or is limited. Overall productivity is very low. The
warm surface water is too buoyant for the cold nutrient rich/very dense water
to have upwelling into the photic zone.
Fish may migrate out of their range to find food as food supplies are
generally low. Here’s a summary of the
conditions.
During La Nina years, the
thermocline is especially weak and productivity may actually increase from
normal years. As La Nina follows El Nino events, fish populations may still be
recovering. These conditions can be
difficult to tell from a normal California winter. Here’s a summary of the
conditions.
In areas
that are polluted or contain stagnant water there may be lower than normal
dissolved oxygen levels. The seabed may be black or dark in color and have a
rotten egg smell. Seawater pulled across these areas may not deliver the
necessary nutrients to the photic zone and productivity may be limited. In
extreme cases, the pH may not be in the normal range. Here’s a summary of the conditions.
6) Harmful Algal Bloom (HAB)
Evidence for
a harmful algal bloom (“red tide”) are a large abundance of dinoflagellates,
lack of other plankton even though we may have a weak thermocline and a healthy
seabed, a brown secchi disk and very poor water clarity.
o
Abundant
dinoflagellates
o
Secchi
disk: brown with very poor water clarity
