Community dynamics of the benthic algae in cobble based streams in South-east Queensland

204 Pages·2017·6.41 MB·English

Community Dynamics of the Benthic Algae in Cobble Based
Streams in South-East Quensland
Author
Tsoi, Wing Ying
Published
2014
Thesis Type
Thesis (PhD Doctorate)
School
Griffith School of Environment
DOI
https://doi.org/10.25904/1912/3287
Copyright Statement
The author owns the copyright in this thesis, unless stated otherwise.
Downloaded from
http://hdl.handle.net/10072/367032
Griffith Research Online
https://research-repository.griffith.edu.au
Community dynamics of the benthic algae
in cobble based streams in South-east
Queensland

Wing Ying Tsoi
BSc, MEnvMgt (Hons)

Australian Rivers Institute
Griffith School of Environment
Science, Environment, Engineering and Technology
Griffith University

Submitted in fulfilment of the requirements of the degree of
Doctor of Philosophy

Sept 2013

Synopsis

Synopsis
Benthic algae are largely present within a polysaccharide matrix called ‘biofilm’ where
they coexist as a community with heterotrophs such as bacteria, fungi and other organic
matter that attaches to substrates. In upland stream ecosystems, benthic algae serve as a
basal food source in riverine food webs and immobilise nutrients from the water column
via the processes of assimilation and remineralisation. From a conservation biodiversity
perspective, upland benthic algal assemblages are not only a biodiversity hot spot for
rare, endangered and endemic freshwater species but also a source of propagules for
downstream reaches.
Diatoms (Division Bacillariophyta) are the most abundant and diverse taxonomic group
commonly dominating the benthic algal communities in upland streams, and are major
contributors to primary productivity providing a particularly high quality food source
compared to other benthic algal taxa and terrestrial matter. The quantity and quality of
benthic diatoms as food sources for consumers in streams change spatially and
temporally can cause resource shortages and dietary shifts in consumers which, in turn,
track these changes to the upper food webs consumers and the benthic food web
patterns. Despite their ecological importance and previous study by taxonomists and
ecologists world-wide, patterns of benthic diatom taxonomic composition and their
underlying factors are largely unexplored in Australian subtropical upland river
ecosystems. Therefore, identification of the biodiversity, distribution and abundance of
diatom taxa that sustain river food webs, is of fundamental importance in understanding
how rivers function as ecosystems.
Given the ecological importance of benthic algal communities, the objective of this
thesis was to investigate mechanisms driving the responses of freshwater biofilm
biomass and diatom community composition to physical and chemical variables in the
Bremer, Logan and Albert catchments in South-east Queensland. Fundamental to this
thesis is the development and testing of a conceptual model of benthic algal community
in upland streams with disturbance (flow), resources availability (nutrient and light) and
stressors (conductivity, pH and turbidity) as the three major physicochemical forces of
the model. A combination of spatial and temporal observational surveys and in-stream
nutrient enrichment experiment were undertaken to test the suitability of the conceptual
model across disturbance, resource and stressor gradients.
i
Synopsis

Firstly, spatial patterns in benthic algal community structure were examined across
three catchments during base flow condition, with an emphasis on relating the spatial
hierarchical interrelationships among ultimate and proximate environmental drivers.
The overall spatial difference observed in the benthic algal community was
predominantly driven by proximate environmental drivers, which in turn were affected
by ultimate drivers. However, no single proximate environmental factor could be
identified as the dominant driver of benthic algal community composition. Flow
conditions across the sites were largely driven by the wet-dry flow gradient that exists
from east to west in the study area. Increasingly flow velocity acted as a drag force,
controlling both biofilm biomass and influencing occurrence of diatom taxa. Nutrients
and light were considered the limiting resources structuring biofilm biomass and the
relative abundance of diatoms. The gradients in stressors such as water conductivity and
pH also played significant roles in shaping the distribution of diatom taxa.
Secondly, the effect of flow on temporal variability in benthic algal communities was
examined over an eight-week high flow variability period, with an emphasis on relating
the multi-scale effects of short-term flow regime, long-term flow regime and associated
changes in local water chemistry (nutrient resources and stressors). A short-term
increase in flow magnitude was the predominant driver of temporal variation in the
benthic algal communities during the study period. In particular, diatom species showed
instant response to increase in flow velocity in which low-profile taxa dominated the
communities during high flow period. Biofilm biomass, diatom richness and diversity
were less sensitive than diatom species to change in velocity but had stronger response
to a range of high flow events in the period up to 30 days prior to any given sampling
occasion. Long-term flow regime and dissolved nutrient concentrations shaped the pre-
event diatom community pattern across sites which determined the site-specific
community resistance during high flow events. Moreover, the result demonstrated that
variation in resistance to flow disturbances can, in part, be explained by attachment
strength of algal taxa and growth form.
The effects of nitrogen (N) and phosphorus (P) enrichment on benthic algal
communities were investigated further by conducting in-stream nutrient diffusing
substrate experiment in high and low ambient nutrient sites. N seems to be the primary
limiting nutrient across sites regardless of the ambient nutrient concentrations. In
general, enrichment relieved nutrient limitation, favouring fewer eutrophic species and
ii
Synopsis

promoted dominance in the community, especially in low ambient nutrient sites with
more oligotrophic species in the species pool. Therefore, low ambient nutrient sites are
potentially more susceptible to enrichment compared with high ambient nutrient sites
because of greater changes in nutrient concentrations in the overlying water. Moreover,
nutrient generalists seem to have higher occurrence among treatments than nutrient
specialists.
The results of this thesis show that the conceptual model is a valid representation of the
benthic algal community in the subtropical upland streams, and is also likely to be valid
for lowland systems. This thesis has shown that proximate factors (local) conditions are
more important drivers of benthic algal community than ultimate (regional) factors. The
relative importance of disturbance, resources and stressors in controlling biofilm
biomass and diatom community composition alternated in space and time. The effects
of nutrient concentrations, light and flow were equally important in the base flow
condition while increased flow magnitude was the dominant driver of the community in
high flow variability period. The gradients in stressors including conductivity and pH
also played significant roles in shaping the distribution of diatom taxa.
This study highlighted the importance of species-based assessments of responses to
nutrient enrichment, as the bulk biofilm biomass responses are quite different from
those at the species level. Moreover, the usefulness of diatom biological traits aids in
creating a more quantitative and predictive approach to establishing relationships
between diatoms and environmental gradients. These mechanisms should allow
environmental managers to select appropriate benthic algal attributes that are likely to
be sensitive to specific environmental changes, to minimise uncertainties associated
with the multiple responses of benthic algal community, to meet management and
monitoring goals.

iii
Statement of originality

Statement of originality

This work has not previously been submitted for a degree or diploma in any university.
To the best of my knowledge and belief, the thesis contains no material previously
published or written by another person except where due reference is made in the thesis
itself.

………………………………………….
Wing Y. Tsoi

iv
Table of contents

Table of contents

Synopsis ............................................................................................................................. i
Statement of originality ................................................................................................... iv
Table of contents .............................................................................................................. v
List of figures ................................................................................................................... x
List of tables .................................................................................................................. xvi
List of appendices ........................................................................................................ xviii
Acknowledgements ....................................................................................................... xix

Chapter 1 General introduction .................................................................................... 1
1.1 Benthic algal communities in upland streams ........................................................ 1
1.2 Roles of benthic algae in upland streams ............................................................... 2
1.3 Theoretical background and benthic algal conceptual models ............................... 4
1.3.1 A community ecology framework: From deterministic to explicit stochastic
models ....................................................................................................................... 4
1.3.2 Benthic algal conceptual models of Stevenson (1997) and Biggs et al. (1998)
.................................................................................................................................. 5
1.3.3 A modified conceptual model of benthic algae in streams .............................. 8
1.3.3.1 Resistance to flow related disturbances ................................................... 10
1.3.3.2 Competition for nutrients and light resources ......................................... 11
1.3.3.3 Tolerance to stressors – pH, Conductivity and Turbidity ........................ 12
1.3.3.4 Biotic interactions .................................................................................... 13
1.3.3.5 Interactions between fundamental forces ................................................ 14
1.4 Benthic algal studies in Australia ......................................................................... 14
1.5 Research objectives and testable hypotheses........................................................ 17
1.6 Thesis structure ..................................................................................................... 20
Chapter 2 Characteristics of study area ..................................................................... 21
2.1 South-East Queensland ......................................................................................... 21
2.2 The Bremer, Logan and Albert catchments .......................................................... 21
2.2.1 Upland streams across the three catchments ................................................. 22
2.2.2 Hydrology and ground water ......................................................................... 26
2.2.3 Geology and vegetation ................................................................................. 27
2.2.4 Land use ......................................................................................................... 28
2.2.5 Reach scale habitats characteristics ............................................................... 29
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Table of contents

Chapter 3 Spatial patterns of benthic diatom community composition and biofilm
biomass in subtropical upland streams and relationships to environmental
variables ......................................................................................................................... 30
3.1 Introduction .......................................................................................................... 30
3.2 Methods ................................................................................................................ 33
3.2.1 Survey Design ............................................................................................... 33
3.2.2 Field methods ................................................................................................ 34
3.2.2.1 Collection of biofilm biomass and diatom assemblage ........................... 34
3.2.2.2 Water quality and environmental variables ............................................. 35
3.2.3 Laboratory methods ........................................................................................ 35
3.2.3.1 Biofilm biomass analysis ......................................................................... 35
3.2.3.2 Diatom identification and counting procedure ........................................ 36
3.2.3.3 Water chemistry analysis ......................................................................... 37
3.2.4 Statistical Analyses ......................................................................................... 37
3.2.4.1 Environmental characteristics ................................................................. 37
3.2.4.2 Diatom summary diversity metrics.......................................................... 38
3.2.4.3 Univariate patterns ................................................................................... 38
3.2.4.4 Multivariate patterns ................................................................................ 39
3.3 Results ................................................................................................................... 41
3.3.1 Environmental characteristics......................................................................... 41
3.3.2 Biofilm biomass .............................................................................................. 44
3.3.3 Diatom community composition .................................................................... 46
3.3.3.1 Summary diversity metrics ...................................................................... 46
3.3.3.2 Species occurrence (presence/absence data) ........................................... 48
3.3.3.3 Species abundance (relative abundance data) ......................................... 54
3.4 Discussion .............................................................................................................. 58
3.4.1 Ultimate variables determine the potential range of flow conditions and
nutrient concentrations ............................................................................................ 58
3.4.2 Proximate variables predominantly driving benthic diatom occurrence ........ 59
3.4.3 Disturbance and resources control biofilm biomass ...................................... 60
3.4.4 Disturbance and stressors control diatom species occurrence and richness .. 61
3.4.5 Nutrient and light resources driving diatom species abundance, evenness and
diversity .................................................................................................................. 64
3.5 Conclusion ............................................................................................................ 65

vi
Table of contents

Chapter 4 Flow disturbance drives temporal patterns in benthic algal community
composition and biomass ............................................................................................. 67
4.1 Introduction .......................................................................................................... 67
4.2 Methods ................................................................................................................ 71
4.2.1 Survey Design ............................................................................................... 71
4.2.2 Field methods ................................................................................................ 73
4.2.2.1 Collection of biofilm biomass and diatom assemblage .......................... 73
4.2.2.2 Hydrological characteristics ................................................................... 73
4.2.2.3 Water quality variables ........................................................................... 76
4.2.3 Laboratory methods ....................................................................................... 76
4.2.3.1 Biofilm biomass analysis ........................................................................ 76
4.2.3.2 Diatom identification and counting procedure ....................................... 76
4.2.3.3 Water chemistry analysis ........................................................................ 76
4.2.4 Statistical Analyses ........................................................................................ 77
4.2.4.1 Environmental variables ......................................................................... 77
4.2.4.2 Diatom growth form ............................................................................... 77
4.2.4.3 Diatom summary diversity metrics......................................................... 77
4.2.4.4 Univariate patterns .................................................................................. 78
4.2.4.5 Multivariate patterns ............................................................................... 79
4.3 Results .................................................................................................................. 80
4.3.1 Environmental characteristics........................................................................ 80
4.3.2 Biofilm biomass ............................................................................................. 84
4.3.3 Diatom community composition ................................................................... 87
4.3.3.1 Summary diversity metrics ..................................................................... 88
4.3.3.2 Species composition ............................................................................... 90
4.4 Discussion ............................................................................................................. 96
4.4.1 Short-term flow variability drives temporal changes in algal attributes ....... 96
4.4.1.1 Decrease in algal biomass in response to 30 days antecedent flow........ 97
4.4.1.2 Dominance of low-profile diatom taxa during high-flow variability
period .................................................................................................................. 98
4.4.2 The long-term flow regime drives site-specific patterns of benthic algal
communities ......................................................................................................... 100
4.4.2.1 Antecedent duration of zero flow events driving changes in richness of
two potential desiccation-resistant genera ........................................................ 101
4.4.2.2 Pre-flow diatom composition determines resistance to high flow
variability .......................................................................................................... 103
4.4.3 The role of nutrients as resources for modulating the effect of flow in shaping
the benthic algal community ................................................................................ 104
4.4.4 Diatom taxa and growth forms respond to flow stress ................................ 105
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