TITLE:
Changes in Ammonium and pH within Intertidal Sediments in Relation to Temperature and the Occurrence of Non-Indigenous Bivalves
AUTHORS:
Leah I. Bendell, Kayi Chan, Sophie Crevecoeur, Charlotta Prigent
KEYWORDS:
Non-Indigenous Bivalves, Temperature, Intertidal, Ammonium, Flood Tide
JOURNAL NAME:
Open Journal of Marine Science,
Vol.4 No.3,
July
31,
2014
ABSTRACT: Our objective was to
determine the role of two invasive bivalves on the concentration of ammonium as
well as pH within intertidal surface sediments (0 - 3 and 3 - 6 cm depth) and interstitial
waters, within the context of a warming environment. To meet this objective we
applied both controlled laboratory (microcosm) and field (mesocosm) experiments
where we varied bivalve presence and absence and sediment temperature. Mesocosm
sampling was tide dependent as we attempted to capture changes in ammonium
concentration and pH as related to flood and ebb tide. We focused on ammonium
as this nutrient is typically a limiting nutrient in oceanic systems and its cycling is a key process that regulates
biological productivity. We also determined pH because of the increasing threat
of ocean acidification. Integration of laboratory
and field studies suggests that bivalves significantly contribute to ammonium
to the intertidal with this amount increasing with increasing temperature. This
ammonium is then released from the sediment as a “pulse” to overlying seawater
on the flood tide. Under laboratory conditions, increased temperature and
density of bivalves decreased overlying water pH. Mesocosm studies suggested some tide dependence of pH with flood
tide acting as a buffer, increasing pH on the flood tide, after sediment exposure
during ebb tide. Increased numbers of invasive bivalves within a warming
environment are likely to increase amounts of ammonium released as a pulse on
flood tides from intertidal ecosystems making this region a source of ammonium
to coastal seas. Greater numbers of non-indigenous bivalves within the
intertidal could also contribute to increased acidity within these regions
although the significance of such increases is unknown.