Cole Greenberg
BIO 250
Jennifer Ma
26 November 2014
False Bay Data Synthesis
Question:
Is eelgrass or ulva more abundant in this mudflat, what implications may this cause?
Methods
In order to obtain this data our class visited Friday Harbors False Bay, a biological
reserve. This “Bay” is so unique due to the drastic physical changes due to tides. This
uniqueness stems the bay’s low tides. Instead of a normal low tide, False Bay transforms
into a terrestrial mudflat ecosystem during low tide. In order to discover the species
diversity of the area our class split into 5 groups. Each group was assigned to a
predetermined test site these sights were as follows: site 1- sandbar, site 2-mudflat, site
3-sand flat, site 4-sandbar site 5-tidepool. Equipped with two shovels, a 1sq meter
quadrat, two buckets, a data sheet and as many warm layers as possible we journeyed
to our test site. At our site we used the 1sq meter quadrat to designate our dig zone.
Immediately after placing the quadrant we counted all of the holes and tubes found in
the areas surface as well as any plant/animal life. We also estimated the % cover of the
entire 1sq meter surface for each sample found. After this, we shoveled the top layer of
soil from the marked 1sq meter into the plastic buckets. From here our groups counted
and documented every species found in the bucket and therefore the 1sq meter
quadrat. All of this was done November 8th 2014 around 11pm.
We documented these species by writing which quadrant and test site was its origin;
we also classified the species based off of physical characteristics. This data was all later
synthesized and the species were identified for the entire beach. For the purpose of my
question, I chose to remove all other species and data that didn’t pertain to plant life
found at False Bay. In order to have an accurate sense of each plants preferred location
and relative abundance, I decided to compare the percent coverage of various plant
species specimens for each quadrant. From this I can observe the relationships between
plants and better, and understand the ecosystem of False Bay.
Percent coverage of Ulva vs Eelgrass
per site
20
18
16
14
12
percent
10
coverage
8
6
4
2
0
Eelgrass
Ulva
1
2
3
Site number
4
5
Fig 1: This is a bar graph showing % coverage of eelgrass and ulva in a 1sq meter site.
We used the data sheet to obtain 1 set of data per si
te.
Fig 2: This figure shows how algae such as Ulva can lead to a depleted ecosystem. Also
this figure shows part of the cultural eutrophication process
Table 1: This is a table showing the characteristics of each site, the presence of eelgrass,
and the species diversity
Substrate
Site 1
Site 2
Site 3
Site 4
Site 5
Fine sand
mud
Fine sand
Sand/mud
Sand/mud
Presence of
Eelgrass?
yes
yes
no
yes
yes
Species >10
yes
yes
no
no
no
Results:
From this experiment we found a huge difference in the population densities of Ulva
and Eelgrass. The high amounts of Ulva when compared to other plant life make ulva
the dominant species in False Bay. Additionally looking at the original group data sheet
we found more species diversity to occur when eelgrass was present. Additionally when
looking at the environment ulva was most abundant in the tide pool quadrants.
Discussion:
The results of this experiment have many possible different causes. I personally think
that the dominance of Ulva in this ecosystem has in turn caused eelgrass populations to
sink. Based off of the fact that Ulva grows best in the tide pool region we can assume it
needs water. One possible reason for the lack of keystone eelgrass species in this
environment is the increased presence of Ulva due to increasing sea levels. As the sea
levels rise all of the ecosystems change, the ulva would be dominant as they have more
water and higher ranges of tolerance. This range of tolerance is obvious; across all
substrate types ulva was abundant. Eelgrass only was found in two of the five-substrate
types. This is advantageous to the ulva because there’s less competition for light.
Additionally when looking above at Table 1 and Figure 1 we can infer that the sites with
2 eel grass plants have more species than those who do not. This may be due to the
phenomenon explained in Figure 2. Finally we can assume that Ulva is overrunning the
eelgrass in False Bay. Because eelgrass is only an indication to the Ulva problem I would
be very interested in doing another study that looks into the dissolved oxygen of these
areas and other symptoms of a uvla spread. Kenji Sugimoto’s study on Ulva’s effect on
eelgrass agrees with my hypothesis. In his study, which consisted of exposing eelgrass
communities to Ulva and comparing these to controls he found Ulva to have a negative
effect on the eelgrasses life. A short synapsis “The objective of this study is to clarify the
effect of ulvoid (Ulva spp.) accumulation on the structure and function of an eelgrass
bed by the coast of Iwakuni, Seto Inland Sea, Japan. We monitored eelgrass shoot
density and volume of ulvoid accumulation in the study site and evaluated effects of the
accumulated ulvoid canopy on the percent survival, seedling density, growth rates,
photosynthetic photon flux density (PPFD) and carbon contents of eelgrass. Eelgrass
shoot density decreased by the accumulation of ulvoid. Also, seedling density decreased
by the increase in the ulvoid volumes. Shoot density, seedling density and leaf
elongation were negatively correlated with ulvoid volume. Carbon contents in eelgrass
decreased by the accumulation of ulvoid (canopy height: 25 cm). These results suggest
that accumulation of ulvoid bloom has significant negative impacts on the structure and
function of eelgrass bed, i.e. decreases in vegetative shoot density, seedling density,
shoot height and growth rate.” These small clues lead
Abstract
This journal article written by Sala L. and R. Mujerigo is very similar to the assumptions I
was making earlier. This article explains the process of cultural eutrophication, or using
up all of the waters nutrients rendering it useless. Instead of examining the source of
cultural eutrophication this article examines the solution to cultural eutrophication.
Sala, L, and R Mujeriego. "Cultural Eutrophication Control Through Water Reuse."Water
Science and Technology : a Journal of the International Association on Water Pollution
Research. 43.10 (2001): 109-16. Print.
Sugimoto, Kenji. "Download PDFs." Effects of Ulvoid (Ulva Spp.) Accumulation on the
Structure and Function of Eelgrass (Zostera Marina L.) Bed. Elsiver, n.d. Web. 26 Nov.
2014.