Table
5.13. Effects of other nonhydraulic dredges on biogenic substrate habitat:
summary of published studies. (S =
statistically significant; citations in bold print are peer-reviewed
publications.)
| No. |
Reference |
Location |
Depth |
Sediment |
Effects |
Recovery |
Approach |
| 1 |
Fonseca et al. 1984 |
Beaufort, North Carolina, USA |
Very shallow, subtidal |
Silty sand with eelgrass |
S
reduction in number of eelgrass shoots and leaf biomass with increased
dredging intensity at each of two sites, one hard bottom and one soft bottom. |
|
Experimental
study with lightweight toothless dredge; two levels of disturbance. |
| 2 |
Langan 1998 |
Piscataqua River, Maine-NH, USA |
Not given |
Oyster bed |
No
detectable differences in the number of benthic invertebrates, species
richness, or diversity; turbidity of near-bottom water doubled 10 m behind
dredge. |
Turbidity
returned to normal 110 m behind dredge. |
One-time
sampling of benthic invertebrates in dredged and undredged sides of the
river; turbidity measured during a single dredge tow. |
| 3 |
Lenihan and
Peterson 1998 |
Neuse River, North Carolina, USA |
3 and 6 m |
Oyster reefs |
Dredging
lowered mean height of 1 m reefs by ~30%. |
|
Experimental
study where 4 of 8 oyster-shell reefs were dredged for 1 wk to remove all
market-sized oysters; sampled 3 days before and 2 days after dredging.. |
| 4 |
Riemann and
Hoffmann 1991 |
Limfjord, Denmark |
Mean depth 7 m, maximum 15 m |
Not given (presumed mussel bed) |
S
increase in suspended particulate matter; S reduction in oxygen immediately
after dredging, especially near the bottom. |
Turbidity
returned to normal within 1 hr. |
Water
column sampling of physical and chemical attributes with a 2-m mussel dredge
before and after dredging (maximum 1 hr) at an experimental and a control
site. |