Akiko Ogawa’s
EFB516 Ecosystems Notes
April 12, 2001 (Thu)
Disclaimer:
These notes are my personal notes. The course instructor or TAs have
no responsibility for the contents or any discrepancies between the materials
presented in the classroom and these notes. You cannot use or refer to these
notes to support or defend your answers on your exams. I suggest you use these
notes to complement your own notes, and not to solely rely on. I would
appreciate your feedback on any part of these notes that I may be misunderstanding.
*** For those who looked at this page before 4/16
(Mon), I corrected my critical mistakes (corrected in red) in the part of “net
source/sink” discussion of this page. Take another look and make sure you
understand it correctly.
Announcements:
Ø Think about the list of “facts” at the
bottom of this page and prepare to answer whether each of them is true or not,
and under what circumstances true.
Lecture topic:
1.
Estuaries (section 6)
2.
Tropical Ecosystems (section 1)
1. Estuaries (section 6)
·
Detritus is
more important for upper levels of food chain? It’s simply not important for
plants. Detritus does not recycle energy to plants. But it has a nutrient feed
back pathway with an amplifier on photosynthesis.
|
|
·
Global
Carbon Cycle
- CO2 enters the surface of
the ocean due to the Coca Cola Effect. In addition, carbon gets stuck down
in the deep ocean due to abduction (?) - movement of parcels of fluid (=
salt water). The only place deep ocean water forms is between Norway and
Iceland – the water is both cold enough and deep enough – where big hunk
of water sinks carrying CO2 together with plankton or whatever
down to the bottom of the ocean. If you drop tracer 14C and
look at the age of water, the water off England = 100 years old, equator =
200 or 300 years, tip of South Africa = 1000 years, across south pole and
near Peru water upwells and contacts with atmosphere up to off of Iceland.
- CO2 from the atmosphere
saturates the surface water down to 200m, in other words, the partial
pressure pushes back up in the same way the partial pressure from the
increased CO2 from the atmosphere pushes down.
Slides
… Dr. Hall’s
Flax pond study continued.
·
Graph of
fish production by species over time: Shows how fish use estuaries. Each fish
species tends to come in estuaries for relatively short time, in August at time
of top productivity. Flounders stay throughout the year. Flounders are abundant
and grow fast.
·
Equation
for calculating the production of higher trophic levels:
p =
b x g, or, average biomass x growth rate of the biomass.
For
example, productivity of flounders = 10g/m2 of flounders x 10%/month
= 1g/m2.
·
(Graph)
Fish weight by age class over the season: How do you get the growth rate? – By
a weight frequency analysis. Record weights of the fish species for each age
class regularly over a season or a year. Then, divide the increase in
production of the same age class over certain period by the number of the days
of the period. However, this calculation does not take into consideration the
loss through predation, etc. This is an important principle to be able to
estimate productivity of higher trophic levels in case, for example, you need
to figure out how much fish you might be allowed to harvest. Although there are
arguments, sustainable fisheries can harvest only 10 to 50% of productivity of
particular species. A study done by John Downy (?) in Quebec found that when
people catch as much as net production, all those fisheries declined. Only when
catch was 10 to 20% of the population, population was sustained.
·
Oxygen
concentration across Flax pond at night: Interior parts of the marsh have lower
oxygen – from mouth to the interior, 3.6, 3, 2, to <1, or even zero if
measured right before sunrise. Yet, we can get a basketful of fish from these
waters. Estuary is extremely demanding, but fish can sustain zero oxygen for
several hours. Some animals have special adaptations - blue crabs half come out
of the water and breathe through gills, many anaerobic organisms that have red
colors – hemoglobin, an oxygen storage device.
·
(Graph) The
growth of the fish: Very low most of the year, very high in summer. Closely
related with primary productivity.
·
Annual
biomass x production graph: Shows linear relationship – the more biomass, the
more total productivity.
·
Flow diagram
– storage and flow: Sun = 1.5 mil. kcal/m2/year, 2500 (= 0.1% of the sun)
captured by plants, 80 (= 3% of plants) fish, and so on.
·
Water
sample collection: water from four incoming tides + four outgoing tides
collected every week for several years.
·
(Graph) Net
Flux of dissolved oxygen over a year at the mouth of channel: Winter = net OUT,
summer = net IN.
·
Heterotrophic
system – 50% detritus-based system. Chemical markers of heterotrophic Flax
pond:
o
Absorbs
oxygen from adjacent ocean – used to process detrital material.
o
Input of
particulate organic material.
·
(Graph) net
INPUT of particulate organic matter (POM) around the growing season.
·
Alluvial
fan at the mouth of the marsh: full of oyster, mussels, i.e., large
concentration of filter feeders removing POM from the incoming ocean water.
·
(Graph) Net
flux of chlorophyll a: consistent net INPUT around the growing season =
phytoplankton are moving in.
·
(Graph)
Nitrate: no clear pattern.
·
(Graph)
Ammonia-N: net OUTPUT = waste products moving out. External subsidy. Food
(phytoplankton) is moving in, getting processed, and is moving out as waste.
Flax pond itself is behaving as if an individual organism. Outwelling
hypothesis was supported by all the data from the Flax pond. Estuaries operate
as highly productive nursery area, by having food sources form the production
in water column, from Spartina, and by using the material from the
adjacent ocean. How does it relate to H.T. Odum’s self-design? What does
ammonia do when it gets out to the ocean? Going out to Long Island Sound and
encourage the growth of phytoplankton. N is generally limiting in coastal
waters. This is a self-reinforcing loop. However, we cannot say more
phytoplankton are coming back to Flax pond because of this N output due to
complex coastal current system – the self-reinforcing loop should be working as
a more giant system. Whether to interpret this as self-design or just an
accidental by-product is up to you.
·
(Graph)
Phosphorus: in summary, P is leaking out into Long Island Sound. PO4
and total P, but not organic-P.
North River
·
Mouth of
North River: net output of ammonia-N was also observed here.
·
Middle
marshes.
·
Upper
marshes.
·
Cattails
marsh: fresh water (middle and upper) marshes don’t operate in the same way.
·
Herring
River: fresh water coming in.
·
Indianhead
River: eutrophic. Draining the area of suburban development of Boston. A lot of
sewage plants and human stuff coming in. Fish ladder.
·
How do you
sample water? Using filter, dry ice, and alcohol so chemical composition
doesn’t change.
·
(Graph)
daily change in concentration of NO3-N, NH3-N, and PO4:
two peaks observed – tidal effect. Nutrient level in the ocean is low. When ebb
tide, water chemistry is affected by sewage plants and other sources. To
identify which water (ocean or river) is affecting the measured concentration,
must test the salinity.
·
Theoretical
graph of nutrient concentration x salinity: the line connects points at highest
salinity (most affected by ocean water) and lowest salinity (most affected by
river water) is the theoretical dilution line. If we assume no biological
activity that affect the nutrient concentration, the points in between should
line up along this line. If the points fall above the line, it means the marsh
is acting as a
net source of nutrients, and if below, as a net sink of nutrients.
|
[Nutrient] Salinity |
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·
(Graph) Nitrogen
concentration x salinity of North River in February (below left – click to blow
up): points are close to the theoretical line.
·
(Graph)
Nitrogen concentration x salinity of North River in summer (below right – click
to blow up): points are mostly far below the theoretical line in the upper part
of the estuary, but ammonia-N and phosphorus at lower part are above the line
of conservative mixing. Upper part is acting as net sink, lower part (salt marshes) is acting as
a source of ammonia and phosphorus. Lower part of
North River is acting the same way as we think Flax pond does.
·
Why nutrient budget is increasingly
important especially in coastal waters? – Everywhere in the world, cities are
built on the coasts. If coastal marshes are net source of nutrients, additional
nutrients from cities = eutrophication of coastal ocean and anoxia.
1. Tropical Ecosystems (section 1)
·
5 (or more)
things about the tropical ecosystems:
o
Higher
diversity
o
Most of
nutrients is stored in vegetation
o
Year-round
sun light
o
Narrow
range of temperature
o
Poor soil
fertility
o
High rain
fall
o
Rapid
decomposition
o
Open and
closed
o
Daily
fluctuation of temperature > annual fluctuation
Are
these true? – Seven of these are incorrect. Under what circumstances are they
true?
Last modified: April
16, 2001 (typos corrected on April 21)
Any comments?
E-mail to akogawa@syr.edu