ECOSYSTEM FUNCTION
EF-03, Intertidal Structure and Function
Code
Title
CHONe_EF-03_CHANK
Potential effects of an invasive bivalve, Nuttallia obscurata, on biogeochemical cycling in the
intertidal
Citation
Kayi Chan*, Leah Bendell-Young (2010) Project EF-03: Potential effects of an invasive bivalve,
Nuttallia obscurata, on biogeochemical cycling in the intertidal resource
Status
Completed
Taxonomic
Coverage
Benthic bivalve community
Scientific Name(s): Nuttallia obscurata, Tapes philippinarum, Protothaca staminea
Geographic
Coverage
Ocean: Northeast Pacific
Local Area: Denman Island, BC
Locality: Fillongley Provincial Park
Spatial
Coverage
Latitude 49º31’59”N
Longitude 124º49’0”W
Temporal
Coverage
Data
Summary
2008 - 2012
Benthic (Bivalve) invertebrates
Benthic bivalve community; Bivalve density; Sediment parameters: grain size, organic matter
content, ammonium and iron concentration, grain size distribution; Water parameters:
ammonimum conetration; Primary Productiviry: Chla; Sorption value (Kd)
The dataset was collected for a MSc thesis and 1 publication.
 Tier I dataset contains abundance of bivalves found in a 0.5x1.0x0.2 m quadrat;
relationship between bivalve density and sediment parameters (organic matter content,
ammonium concentration, and grain size distribution) as determined by Pearson
correlation coefficients for the surficial and mid depths of sediment cores; sediment
characteristics that best determined bivalve densities were determined using a maximum rsquare improvement procedure for the surficial and mid depths of sediment cores.
 Tier II dataset contains changes to sediment parameters (organic matter content,
ammonium concentration, iron concentration and grain size distribution) in relation to
varying varnish clam densities for the surficial, mid and lower depths of sediment cores. In
addition, ammonium concentrations, iron concentrations and chlorophyll a concentrations

were determined for surficial sediments to examine the potential effects of these nutrients
on an observed algal bloom.
Tier III dataset contains the ammonium concentrations found within the water and
sediments as well as the sorption value (Kd) calculated from these two parameters for the
microcosm experiment.
Abstract
The varnish clam, Nuttallia obscurata, is a rapidly spreading invasive species that can reach high
densities (i.e. 800 individuales m-2). A three-tiered approach involving a field survey (Tier !), a
density manipulation experiment (Tier II) and a microcosm experiment (Tier III) was applied to
determine the effects of this invasive bivalve on biogeochemical cycling in the intertidal zone. At
natural densities, bivalve distribution was best explained by sediment grain size. High densities of
varnish clams did not significantly increase organic matter concentrations; although the ability of
varnish clams to deposit feed and bioturbational activities may have prevented accumulations.
High densities of varnish clams resulted in significantly higher concentrations of ammonium and
precent silt. Nitrogen is a limiting nutrient with ammonium preferentially used by phytoplankton
and microphytobenthos. These primary producers form the basis of all marine food webs; thus,
changes in the concentration and flux of ammonium may impact ecosystem functioning of
intertidal areas.
Credit
Research is sponsored by the NSERC Canadian Healthy Oceans Network.
Descriptive
Keywords
Field, Laboratory, In situ experiment, Laboratory experiment, Nuttallia obscurata, invasive
bivalves, intertidal, nitrogen, biogeochemical cycling
Related
Publications
1. Chan K. (2012) Effect of an invasive bivalve (Nuttallis obscurata), on biogeochemical
cycling in the intertidal. MSc. Thesis August 2012
2. Chan K., Bendell L.I. (2013) Potential effects of an invasive bivalve, Nuttallia obscurata, on
select sediment attributes within the intertidal region of coastal British Columbia. J Exp Mar
Bio Ecol: 444: 66-72
3. Chan K, Bendell L.I. (in prep) Ammonium excretion in varnish and manila clam and its
importance to nitrogen in the intertidal. Journal of Experimental Marine Biology and
Ecology.
Scientific
Contacts
Data Centre
Leah Bendell-Young and Kayi Chan
Access and
Usage
Visit Canadian Healthy Oceans Network website
Canadian Healthy Oceans Network / CHONe@mun.ca
Get Metadata and Data