Food web properties of the recently constructed, deep subtropical Fei-Tsui Reservoir in comparison with the ancient Lake Biwa
Hydrobiologia
Food web properties of the recently constructed, deep subtropical Fei-Tsui Reservoir in comparison with the ancient Lake Biwa
Handling editor: Michael Power 0 1 2 3 4
0 K. Fukumori Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies , Tsukuba 305-8506 , Japan
1 Y. Sakai Lake Biwa Environmental Research Institute , Otsu 520-0022 , Japan
2 N. Okuda (&) Research Institute for Humanity & Nature , Kyoto 603-8047 , Japan
3 F.-K. Shiah (&) Research Center for Environmental Changes , Academia Sinica, Taipei 115 , Taiwan
4 S.-M. Yang C. Hsieh Institute of Oceanography, National Taiwan University , Taipei 10617 , Taiwan
Using carbon and nitrogen stable isotope analysis, we characterised food web properties of the deep subtropical Fei-Tsui Reservoir (FTR), which was recently altered from a lotic to a lentic system after dam construction. In the littoral zone, zoobenthos showed strong reliance (83.9%) on benthic algal production. Zoobenthos were never found in the profundal zone because of anoxia. Zooplankton depleted 13C more than that of particulate organic matter as their putative food source, suggesting a contribution of methane-derived carbon to pelagic food webs. Excluding juveniles, non-native and fluvial species, adult fish showed strong reliance (on average 80.9%) on benthic production, weakly coupled with pelagic food webs. These results contrast low benthic production reliance (on average 27.4%) for a fish community in Lake Biwa, which is also classified as a subtropical lake. Both lakes are characterised by deep pelagic waters but quite different in their geological ages, suggesting that the aquatic communities in the FTR have fluvial origins, and their lacustrine history was too short for them to adapt to newly emerged deep pelagic habitat. Our isotope data are useful as a reference of newly established lentic food webs to monitor ongoing ecological and evolutionary dynamics as a result of anthropogenic disturbances.
Dam construction; Production reliance; Stable isotope analysis; Trophic flow; Trophic position
Introduction
Dams and reservoirs have been constructed to meet
accelerated demands for water and energy resources as
populations experience explosive growth and climate
change worldwide
(Nilsson et al., 2005)
. While dams
provide high public utility, they can negatively impact
river ecosystems by drastically changing waterway
from lotic to lentic systems
(McAllister et al., 2001)
.
In dammed rivers, some taxa can modify and adapt
their life histories to sustain their populations;
however, others that cannot adapt may go into local
extinction due to loss of original habitats. At present,
dam construction is considered as one of the major
drivers of biodiversity loss in the freshwater
ecosystems through the alteration and homogenisation of
natural hydrological regimes
(Poff et al., 2007)
, the
creation of physical barriers to migratory species
(Liermann et al., 2012)
, the dispersal and colonisation
of non-native lentic species
(Havel et al., 2005)
, and
the pollution and eutrophication at dam sites
(Dudgeon, 2000)
. Therefore, it is important to perform
ecosystem assessments after dam construction for
water quality management and biodiversity
conservation.
Stable isotope analysis (SIA) is a powerful tool to
assess ecosystems, especially food web properties
characterised by trophic interactions within a
biological community. Food web characterisation is of
ecological and social significance because trophic
interactions can drive nutrient cycling and energy
flows, which in turn affect ecosystem services (e.g.
water quality, food supply for humanity). At present,
the stable isotopic approach is the preferred method for
studying aquatic food webs, in which carbon (d13C)
and nitrogen (d15N) isotope ratios, for aquatic species,
are used to distinguish primary trophic pathways, for
example, pelagic versus littoral pathways
(France,
1995a, b)
or aquatic versus terrestrial pathways
(Peterson & Fry, 1987; Finlay, 2001)
. Especially for
fish, their isotopic signatures provide useful
information in estimating the relative importance of trophic
energy flows in lake ecosystems. Fish predators
integrate a variety of trophic pathways as they couple
pelagic and littoral food webs due to their high mobility
and omnivory
(Vander Zanden & Vadeboncoeur,
2002; Vander Zanden et al., 2011)
. The stable isotopic
approach can also be applied to assess food web
alterations in aquatic ecosystems under human
disturbances
(Vander Zanden et al., 1999; Layman et al.,
2007; Anderson & Cabana, 2009; Hamaoka et al.,
2010)
. In most cases, however, stable isotopic studies
are conducted after ecosystem alterations were
perceived. As such, limited information is available on
original conditions before the disturbance
(but see
Okuda et al., 2012; Vander Zanden et al., 2003)
.
Newly constructed dams and reservoirs provide a
good possibility to unders (...truncated)