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A long-term study of a small rocky reef

A long-term study of a small rocky reef. Bill Ballantine Leigh Marine Laboratory New Zealand. My results are ONLY interesting because of the circumstances in which they were gathered. The background is highly relevant. NZ is at the centre of the water hemisphere.

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A long-term study of a small rocky reef

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  1. A long-term study of a small rocky reef Bill Ballantine Leigh Marine Laboratory New Zealand

  2. My results are ONLY interesting because of the circumstances in which they were gathered. The background is highly relevant.

  3. NZ is at the centre of the water hemisphere

  4. On land, the concept of NATURAL has no scientific meaning in most places. But NZ was the last place people found (only ~ 700 years ago) So in NZ, natural does have scientific and practical meaning. NZ National Parks aim to ‘’keep these areas as natural as possible’’. New Zealanders can transfer the idea into the sea - where it works even better. In the sea,natural is a valid scientific concept.

  5. TIME is the most neglected factor in ecology The practical reasons are obvious, but these are reinforced by various implicit assumptions which may not be valid. The main exceptions are: (a) exploited species (e.g. fisheries) (b) recovery from disturbances (e.g. cyclones) (c) successional changes (e.g. salt marshes) None of these provide data on the unforced changes that may occur in biological communities (i.e. the intrinsic or natural variations).

  6. This study aims to determine the variations over TIME in a NATURAL biological community i.e. where there is no exploitation, no serious disturbance and no driving force for change. To make this valid, practical and generally meaningful requires a large number of decisions, choices, stratifications, etc. including -

  7. Theoretical points: 1. If we are making spatial comparisons the observations need to be made at the same time. Similarly, comparisons over time need observations at the same place. The study needs a fixed site. 2. Replicates in space need to be separated by sufficient distance to avoid auto-correlation (pseudo-replication). Similarly, replicates in time need sufficient separation in time. The study must extend over multiple generations.

  8. Practical considerations: • No human interference : an isolated reef in a marine reserve • No major natural disturbances (e.g. erosion) • Easilyaccessible for frequent observations • Simple topography – uniform, gentle, bedrock slope • Fixed or reduced secondary factors (e.g. rock type, salinity, etc.) • Low biological diversity – only ~15 ecologically significant species • Short generation times – < 1 - 5 years • Good biological information on all species • Comprehensive – all significant species monitored • Small enough to allow census of most species (no sampling errors) • Large enough to provide multiple patch dynamics

  9. Generality • A simple but ordinary and typical situation, which lacks any special features that might cause changes. • A central position in the general ecological framework for rocky shores defined by the main driving forces – vertical height and wave action.

  10. The locality: Goat Island Bay, Leigh EchinodermReef

  11. Echinoderm Reef

  12. Zonation / wave exposure diagram for the NE coast of New ZealandExposed Uniform bedrock slopes only Sheltered Echinoderm Reef For details see J.E. Morton (2004) Seashore Ecology of N.Z. and the Pacific page 79

  13. Standard Reef: total area 5m x 4m

  14. Zonation / wave exposure diagram for the NE coast of New ZealandExposed Uniform bedrock slopes only Sheltered Standard Reef

  15. Standard Reef: 1–20 @ 1m2, A-L @ 0.1 m2 Most data that will be shown comes from 1-10 m2

  16. Square 2 : open rock and crevices

  17. A. Four mollusc speciesgrazing on hard surfaces Residents Sypharochiton pelliserpentis (chiton) Cellana radians (patellid limpet) Visitors Turbo smaragdus (turbinid snail) Melagraphia aethiops (trochid snail)

  18. Wave Exposure Diagram for NE New Zealand DOMINANT and sub-dominant grazing MOLLUSCSExposedSheltered Standard Reef

  19. Zonation / wave exposure diagram for NE New Zealand DOMINANT and sub-dominant grazing MOLLUSCSExposedSheltered Sypharochiton Melagraphia Cellana radians Standard Reef Standard Reef Turbo smaragdus

  20. Sypharochiton pelliserpentis

  21. Sypharochiton pelliserpentis Homing to crevices (< 30 cm) Slow growing and long-lived (>3 years) Small changes (<10% per month and <50% per year) No seasonality Range of biomass over time ~ 4x

  22. * mean *As total wet weight

  23. Cellana radians

  24. Cellana radians Home-ranging (< 1 m) Fast growing and short-lived (< 2 years) Rapid changes (up to 50% per month) Strong seasonality (summer peaks) Range of biomass over time >20x

  25. mean

  26. Turbo smaragdus (turbinid)

  27. Turbo smaragdus Wide-ranging (up and back to lower zone) Moderate growth rate and longevity Very rapid short term changes (>50% per month) and rapid changes per year >70%) Weak seasonality Range of biomass over time >20x

  28. Melagraphia aethiops(trochid)

  29. Melagraphia aethiops Very wide-ranging (at this level) Moderate growth rate and longevity Long periods of low (< 30) or high (> 50) abundance No seasonality Range of biomass over time >20x

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