Flow Influences on Particulate Organic Matter Settlement Within Tidal Creek Mudflat and Oyster Reef Habitats

1
Flow Influences on Particulate Organic Matter
Settlement Within Tidal Creek Mudflat and Oyster
Reef Habitats Young, Ginger, Mauldin, Ashley and
Walters, Keith, Department of Marine Science,
Coastal Carolina University, Conway, SC 29528

• There were no significant habitat by day (F 3,30
  2.87, p gt 0.05), habitat (F 1,30 0.11, p gt
  0.05) or day (F 3,30 1.53, p gt 0.05)
  effects on the settlement of POM total carbon gt
  63 µm (Fig 4).

Abstract
The small-scale (m) effects of tidal flow on
particulate organic matter (POM) settlement
within intertidal mudflat and natural oyster reef
habitats were examined as part of a long-term
study focusing on oyster reef restoration in
South Carolina. POM settlement was considered an
indirect measure of total water column food
availability that affects growth and survival of
oysters on developing reefs. The study was
conducted within a Waites Island, SC tidal creek
at mudflat and adjacent natural oyster reef
sites. Sites were located in close proximity to
ongoing experiments examining the suitability and
spatial arrangement of different hard substrate
types (e.g., shell clutch, cement-covered stakes)
for oyster reef restoration. POM settlement data
were collected over 24 h periods for 5 d during
spring tides using replicate settlement traps.
Tidal flow was determined indirectly over the 5 d
period with dental plaster clod cylinders.
Ash-free dry weight values were determined from
settlement trap samples. Mudflat and oyster reef
habitat settlement differences resulted from
different amounts of suspended POM in the water
column and not different rates of flow between
sites.
Close-up of Settlement Traps w/ the Mud Site
Clods, Platforms Settlement Traps w/ the Reef
Site
Results

• There was no significant difference in the daily
  loss of plaster from clods between mud and
  reef sites (F 1,17 2.1, p gt 0.05) - no
  difference in flow between sites (Fig1).

Figure 4 Total POM carbon collected (mean SE)
in settlement samplers for the gt63µm fraction.

• There was a significant habitat by day
  interaction (F 3,30 4.66, p lt 0.01) in the
  settlement of lt 63 µm total POM carbon (Fig 5).
  

Objective
To determine if there are significant flow and
POM settlement differences between mudflat and
oyster reef habitats.
Figure 1 The mean (SE) daily erosion of plaster
(hydrodynamic flow) at mud and reef sites.
Tidal Creek

• There were no significant habitat by day (F 3,30
  0.06, p gt 0.05), habitat (F 1,30 0.31, p gt
  0.05) or day (F 3,30 2.20, p gt 0.05) effects
  on the total settlement of material gt 63 µm
  (Fig 2).

Map shows an aerial view of the tidal creek study
site
Figure 5 Total POM carbon collected (mean SE)
in settlement samplers for the lt 63µm fraction.
Conclusions
Waites Island tidal creek study site with
ongoing clutch bag and stake reef restoration
treatments shown

• Mud and reef differences in the settlement of
  POMl could not be explained by differences in
  flow characteristics between the sites.
• Settlement of lt63 µm POM, both total and
  organic carbon amounts, was effected by habitat
  and date. These results could represent the
  effects of daily or tidal differences in flow
  and/or could represent actual differences in
  the amount of POM passing over each site.
• Our results suggest, but do not confirm, that
  oyster reef restoration success may depend on
  the initial habitat in which the reef is being
  established because of habitat effects on POM
  availability.

Figure 2 Total settlement dry mass per day (mean
SE) for the gt63µm fraction.

• There was a significant habitat by day
  interaction (F 3,30 3.05, p lt 0.045) in the
  settlement of the total material lt 63 µm (Fig
  3).

Materials and Methods

• The analysis of flow within the study site was
  measured using the clod card protocol (see
  Judge pers. com.) -Clods (2 ea.) were mounted on
  5 platforms positioned flush with the sediment
  in mud and reef sites -Clods were collected
  after 5 d -The difference in clod mass was used
  as an indirect measure of flow
• POM settlement was measured using 50 ml tubes
  placed w/ mud and reef sites -5 tubes
  haphazardly placed and recovered at low tide w/
  each site every day for a total of 5 d -Tubes
  were pushed into the sediment at each site
  leaving ca. 2 mm above the surface -Each tube
  was filled with seawater -Samples were frozen _at_
  -20 ºC until processed -Sediments were divided
  into gt and lt63µm fractions -Fractions were dried
  _at_ 60 ºC, weighed, and ashed _at_ 500 ºC,
  reweighed to determine total dry and POM mass
  of the settled material
• All results were analyzed using SAS

Figure 3 Total settlement dry mass per day (mean
SE) for the lt63µm fraction