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  Services » Publications » Technical reports - by year » tr201131

Tairua Estuary shellfish and benthic habitat mapping and assessment of sediment contamination (2009/10)

On this page: Abstract, table of contents

Report: TR 2011/31

Author: M Felsing & H Giles

Abstract

Shellfish are major components of estuarine communities. Apart from their value as a food resource, shellfish perform important ecosystem services.

Although relatively resilient compared to other types of intertidal biota, shellfish populations may be sensitive to a number of pressures associated with human activities, including sediment contamination. This project aimed to map the distribution and abundance of three species of shellfish in Tairua Estuary: the cockle (Austrovenus stutchburyi), the pipi (Paphies australis) and the wedge shell (Macomona liliana). The distributions of estuary sediment types, estuarine vegetation and sediment trace elements and organic compounds were also mapped.

Tairua Estuary shellfish and benthic habitat mapping and assessment of sediment contamination (2009/10) (7 mb)

Table of contents

  Acknowledgement i
  Executive summary v
1 Introduction 1
1.1 Benthic shellfish and habitat mapping project background 1
1.2 Benthic shellfish and habitat mapping project objectives 2
1.3 Assessment of sediment contamination 2
1.4 Tairua Estuary 2
2 Methodology 5
2.1 Benthic shellfish and habitat mapping 5
2.1.1 Sampling and sample analyses 5
2.1.2 Statistical analysis 6
2.2 Assessment of sediment contamination 7
3 Results 9
3.1 Overview 9
3.2 Sediments 9
3.2.1 Substrate classification and grain size analysis data 9
3.2.2 Comparison of the two sediment assessment methods 10
3.2.3 Comparison of substrate categories with redox potential discontinuity layer 12
3.3 Bivalves 15
3.3.1 Bivalve abundance and distribution 15
3.3.2 Bivalve size classes 19
3.4 Estuary vegetation 23
3.5 Relationships between sediment properties, vegetation and bivalve presence densities 25
3.5.1 Bivalve abundance at sites with different sediment properties and vegetation cover 25
3.5.2 Regression trees to predict shellfish abundance from environmental data 28
3.5.3 Relationships between bivalve community structure and environmental variables 31
3.6 Assessment of sediment contamination 33
4 Summary and discussion 33
4.1 Sediments 33
4.2 Bivalve abundances 34
4.3 Relationship between bivalve presence and abundances and sediments and estuarine vegetation 35
4.4 Evaluation of habitat mapping and suggestions for improvment of methods 36
4.4.1 Bivalves 38
4.4.2 Vegetation 38
4.4.3 Sediments 38
4.5 Assessment of sediment contamination 40
5 Conclusion 40
6 References 42
  Appendix 1 - Sample point maps 44
  Appendix 2 - Field sampling sheet 46
  Appendix 3 - Wentworth sediment classification 47
  Appendix 4 - Statistical analyses used to compare substrate categories and sediment grain size 48
  Appendix 5 - Shepard's diagram for sediment classification 51
  Appendix 6 - Trace elements and organic compounds 52
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