Fróðskaparrit - 01.01.2009, Síða 162

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CHEMICAL SEDIMENT VARIABLES FROM THE FAROE AREA:
ORCANIC CONTENT, NITROCEN, PHOSPHORUS, ZINC, AND COPPER
Introduction
As part of the marine environmental moni-
toring program instituted by the Faroese
government, Kaldbak Marine Biological Lab-
oratory (KMBL) has conducted about 40
seabed sampling surveys a year since 1998.
The samples were analyzed for selected
chemicals, pH and redox-potential of the
sediment, as well as macro fauna and other
more descriptive variables. The chemical
variables analyzed were: organic content in
the sediment expressed as loss on ignition
(LOI), total nitrogen, total phosphorus, zinc
and copper. This paper will give an overview
of the chemical variables in relation to depth
and to sediment type.
The environmental monitoring sampling
program included sites that were heavily im-
pacted by local outlets of organic materials
(especially from salmon farms) and sites of
no or little impact. The present paper only
deals with reference stations and stations
that were expected to be natural or with no
known impact source.
LOI, nitrogen, phosphorus, zinc and cop-
per are used by the Faroese Environmental
Protection Agency as restrictive indicators of
the maximum allowed environmental im-
pact on the seabed. In this paper, the authors
present an overview of the general range in
which these selected chemicals are found, as
they are in the top two centimeters of soft
bottom sediments from a wide selection of
sampling stations in Faroese inshore loca-
tions.
To give a more complete picture of the
chemical range in which these selected
chemicals are found in the whole of the
Faroe area, we have also included previously
reported data from shallow waters (Bloch et
al„ 1986; Caard, 1990; Hoydal and Dam, 2004;
Johansen, 2006) and deeper waters (Grøsvik
et ai, 2000; Josefson, 2001; Mannvik and Pe-
tersen, 2002; Kaldbak Marine Biological Lab-
oratory, 2006)
The combination of a complex topogra-
phy, different water masses and different
current systems make the seabed fabric in
the Faroe area difficult to describe. An
overview of the current systems of this area
can be found in Hansen and Østerhus
(2000). Inside the fjords, soft sediments can
be found only in the deepest parts, while the
slopes from the seashore towards the mid-
dle of the fjord can be a mixture of all types
of sediments, changing over only short dis-
tances. Information on Faroese inshore
seabed features is scarce, but a general de-
scription of the Faroe area can be found in
Bruntse and Tendal (2001). Tendal et al.
(2005) describe the area thus: "The crude
picture is that of very mixed gravelly bot-
toms sometimes with rocky outcrops on the
shelf and slope, and better sorted bottoms
with decreasing grain size at larger depths. A
substantial component on all bottoms is de-
bris deposited during the last ice age (Waag-
stein and Rasmussen, 1975). On the plateau,
shell fragments of many sizes are abundant,
sometimes giving the bottom the character
of shell-gravel or shell-sand. Soft bottoms are
found in the fjords and in a few depressions
on the outershelf.
The overall aim of this paper is to de-
scribe the natural variation of organic con-
tent (LOI), nitrogen, phosphorous, zinc and
copper in marine sediments from the Faroe
area.