Ageing methods for protected deep-sea corals: a review and recommendation for an ageing study Prepared for DOC February 2018 Prepared by: Di Tracey, Helen Bostock, National Institute of Water & Atmospheric Research (NIWA), Megan Shaffer, Victoria University of Wellington, (VUW) For any information regarding this report please contact: Di Tracey Scientist Deepwater +64-4-386 866 [email protected] National Institute of Water & Atmospheric Research Ltd Private Bag 14901 Kilbirnie Wellington 6241 Phone +64 4 386 0300 NIWA CLIENT REPORT No: 2018035WN Report date: February 2018 NIWA Project: DOC18303 Quality Assurance Statement Reviewed by: Peter Horn Formatting checked by: Pauline Allen Approved for release by: Rosemary Hurst Cover image: Solitary colony of Bathypathes in situ, Louisville Ridge [Deep towed Imaging System, NIWA] Reference: Tracey, D., Bostock, H., Shaffer, M. (2018). Ageing methods for protected deep-sea corals: A review and recommendation for an ageing study. DOC Contract 4527 GMC - Age & Growth of coral (POP2017-07). NIWA Client Report No. 2018035WN 40 p. © All rights reserved. This publication may not be reproduced or copied in any form without the permission of the copyright owner(s). Such permission is only to be given in accordance with the terms of the client’s contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Whilst NIWA has used all reasonable endeavours to ensure that the information contained in this document is accurate, NIWA does not give any express or implied warranty as to the completeness of the information contained herein, or that it will be suitable for any purpose(s) other than those specifically contemplated during the Project or agreed by NIWA and the Client. Contents Executive summary ............................................................................................................. 4 1 Background ............................................................................................................... 5 2 Section 1: Ageing methods for protected deep-sea corals: A review ............................ 6 2.1 Introduction .............................................................................................................. 6 2.2 Age and growth methods ......................................................................................... 9 2.2.1 Direct observations ................................................................................................... 9 2.2.2 Enumeration of growth bands ................................................................................ 10 2.2.3 Radiometric analyses .............................................................................................. 11 2.2.4 Amino acid racemization ........................................................................................ 15 3 Section 2: Recommendations ................................................................................... 15 3.1 Selected study species and methodology............................................................... 16 3.2 Complementary research ....................................................................................... 17 4 Acknowledgements ................................................................................................. 18 5 References ............................................................................................................... 19 Appendix A Summary of current age and growth data for deep-sea corals, adapted from Tracey et al. 2013 and Clark et al. 2014. ............................................................ 27 Appendix B Advantages and disadvantages for ageing methods, with protected coral groups for which method was successfully applied. .......................................... 34 Figure Figure 3-1: Distribution map for the New Zealand region of the two black coral species proposed to be aged: Bathypathes species, B. patula and B. alternata. 18 Ageing methods for protected deep-sea corals: a review and recommendation for an ageing study Executive summary Deep-sea corals are a highly diverse group of marine organisms several of which are characterised by their overall slow growth and extreme longevity. Due to their fragile forms, skeletal composition, and location, they are vulnerable to various anthropogenic threats with some groups expected to have little to no ability to recover. Impacts include; fishing such as bottom trawling and bottom long-lining, mineral exploration and deep-sea mining. There are also the environmental impacts predicted from climate change including sea water warming and ocean acidification. To better inform risk assessments for these deep-sea corals, a knowledge of their age and growth is key to understanding coral regeneration times following trawl disturbances or other damage. This report presents outputs for year one of the Conservation Services Programme, Department of Conservation Project POP2017- 07, and includes a literature review describing the methods to age coral species and a recommendation to obtain accurate age and growth data for a key protected coral species. We review the main methods applied to measure age and growth of deep-sea corals. These can be split into three key applications: (1) direct observation e.g., in situ measurements or in-aquaria experiments of linear growth or surface extensions; polyp addition rate; estimation of calcification rates (e.g., using the buoyant weight technique), (2) enumeration of skeletal growth bands and (3) radiometric analyses. The advantages and disadvantages of each method are reviewed. Overall (1) direct observation studies were few, due to time constraints and cost of research in the deepsea; (2) growth band counts were not valuable for certain coral species with porous skeletons, hollow branches, or colonial matrix-like morphologies (e.g., gorgonian bubblegum corals and branching stony corals), but were appropriate for corals containing clear banding patterns in cross section (e.g., gorgonian octocorals such as bamboo corals; and some stony cup corals); and (3) radiometric analyses had been applied to several coral groups, but success of the dating techniques (i.e., radiocarbon (14C) vs. lead 210 (210Pb) vs. uranium / thorium dating (U/Th)) is dependent upon local environmental conditions and the carbonate mineralogy of the coral. We recommend next steps for coral ageing research in the New Zealand region and detail a method most appropriate to apply to obtain accurate age and growth data for a previously determined ‘High Risk’ protected coral species, specifically the Antipatharian black coral genus Bathypathes (Family Schizopathidae). The analytical method we propose is radiocarbon (14C) dating of base and tip regions of the colony combined with growth ring counts from around 10 basal sections for selected specimens of species B. alternata or B. patula. The micro-milling of material, and the interpretation of results would be carried out in Year 2 of the project. The recommendations build on the recent risk assessment that identified deep-sea species such as black corals (at the order level Antipatharia, and the genus Bathypathes), and the gorgonian coral genus Paragorgia, as being at high risk from the effects of bottom trawling. Most reef-building scleractinian corals, as well as other gorgonian coral taxa, were assessed as medium risk, and cup corals and hydrocorals were relatively low risk. These results were consistent with expectations based on the form and biology of the corals, their depth and distribution patterns, and knowledge of trawling impacts, both past and predicted. The research will address the risk assessment recommendations. 4 Ageing methods for protected deep-sea corals: a review and recommendation for an ageing study 1 Background Knowledge of the age and growth of protected deep-sea coral species (also referred to as cold-water corals) for the New Zealand region has been identified as key to understanding coral regeneration times following trawl disturbances (Williams et al. 2010) or other damage. Regeneration of fauna relates to the time that would be required for a colony to grow back to its unfished state. Coral form and ecological sensitivity are important components of defining the risk of impacts, and therefore protected deep-sea coral groups need to be aged to inform future risk assessments and the development of appropriate management options for these groups. As part of an earlier Conservation Services Programme (CSP), Department of Conservation (DOC) Project POP2013-05, a pilot ecological risk assessment (ERA) for protected corals in New Zealand was developed by Clark et al. (2014). The risk assessment examined the extent of the impact due to the fishing activity (determined by the susceptibility of the unit to the fishing activities), and the productivity of the unit which determines the recovery potential. Susceptibility of the corals is assessed by three aspects (availability, encounterability, and selectivity), and a single productivity aspect. Risk assessments such as these are key tools for informing management approaches for protected corals in that they provide a better understanding of the various aspects and characteristics of coral species and the fisheries that contribute to risk determination. Also under the CSP POP2103-05 project, Anderson et al. (2014) predicted the distribution of protected deep-sea corals in relation to areas where they are at risk of interactions