Flowering patterns for in Raglan Harbour

Willemien de Kock1, Fleur Matheson2 and Chrissen Gemmill1 1University of Waikato and 2National Institute of Water and Atmospheric Research (NIWA)

Zostera muelleri is a marine flowering native to New Zealand. This species of seagrass has a vast longitudinal distribution, from New Zealand to Papua New Guinea, inhabiting a variety of habitats from virtually sub-Antarctic to tropical waters. are highly important ecologically, not least because they serve as a nursery ground for juvenile fish. muelleri is NZ’s only species of seagrass. There is currently a lack of knowledge about the reproductive strategies of this species of seagrass, particularly surrounding flowering and seed production. Figure 1: Map showing sampling sites in Raglan Harbour. Figure 2: Seagrass patches at the Campground site in the Raglan Harbour. Our objectives were –– To investigate the flowering habits of Zostera muelleri at sites in Raglan Harbour (Figures 1 and 2). –– To examine sediments around seagrass patches for Zostera muelleri seeds. –– To examine the influence of water quality and clarity and plant density and size on flowering. Methods In the field: Monthly (November to January) at each site: 1. Three quadrat locations selected, representative of plant cover range. 2. Assess cover, count inflorescences, cores for biomass and seeds (Figure 3). Figure 3: Field work included measurements of inflorescence numbers, taking biomass and sediment cores 3. Logger deployment to measure light continuously (three sites only). at each site. Inset showing quadrats (0.25 m2) were used to determine the percentage of seagrass cover. 4. Water sample for salinity, turbidity and nutrients (Table 1). -1 -1 In the lab: Site Salinity (ppt) Turbidity (NTU) DIN (ug L ) DIN (ug L ) 1. Leaf size measurements. Opotoru 29 (±2) 36 (±1) 86 (±5) 23 (±2) 2. Root and shoot biomass. Bridge 27 (±0) 25 (±3) 95 (±14) 23 (±4) 3. Sieving sediment and microscope examination for seeds (c. 2 mm x 1 mm size). Campground 29 (±1) 36 (±10) 77 (±27) 18 (±2) Info Centre 26 (±0) 56 (±27) 107 (±9) 17 (±3) Cliff St 34 (±0) 18 (±2) 55 (±19) 22 (±2) Results Wallis St 33 (±0) 253 (±225) 60 (±21) 29 (±2) • Flowers were associated with: Daisy St 23 (±1) 250 (±176) 59 (±15) 30 (±8)

–– higher plant cover (≥75% cover) (Figures 4 and 5) Table 1: Mean (± standard error) values for water quality parameters for all sites. –– higher biomass (≥650 g m-2), especially roots (Figures 4 and 5) –– larger leaf size, especially width (Figure 4) 92 900 80 )

Mean - 2 –– lower salinity (Figure 4). ) )

Mean±SE 2

m 70 - Mean±0.95 Conf. Interval

88 800 n ( ( % 60 y t i

• No significant relationships with water quality (but limited spot data). e r ( g m s v

84 s 50 n

o 700 e c d

40 s

• Photosynthetic light mostly above minimum growth requirements at all sites 80 e s c o m a s 600 n 30 e

(limited data) (Figure 6). c 76 s 20 t-test 500 t-test e o r S e a g r l R o t b i 72 f 10 • Observations of more flowers in areas with seeps, streams and tide pools. p=0.049 p=0.017 n I 400 0 • No seeds were found. No Yes No Yes 0 20 40 60 80 100 Flowers present Flowers present Seagrass cover (%)

80

2.8 ) 32 - 2 m 70

2.7 n

Conclusions ( 60 y t

30 i m ) 2.6 s 50 n e To our knowledge this is the ( p t ) d

t y d t h ( 28 40 2.5 e n i c i first record of Zostera muelleri n 30 e c

S a l 26 2.4 s 20 e flowering in Raglan Harbour. L e a f w i

M-U test t-test o r l 24 f 10 2.3 n p=0.074 p=0.146 I Our results support previous 0 No Yes No Yes 0 400 800 1200 1600 2000 findings in Tauranga Harbour Flowers present Flowers present Total biomass (g m-2) that flowering by this species is Figure 6: Mean daily light as PAR (photosynthetically AQRF162 as at 30/06/2016. project for NIWA was designed by Aarti layout The poster Wadhwa available radiation) measured at each site. plant density and size dependant, Figure 4: Comparison of plant and water attributes for plots with and without flowers. Figure 5: Relationships between plant attributes and inflorescence density indicating potential thresholds and associated with conditions keeping wet. (red dashed line).

Acknowledgements: This research was carried out with a University of Waikato summer student scholarship and was also supported by the Ministry for Business, Innovation and NIWA – enhancing the benefits of New Zealands natural resources Employment Aquatic Rehabilitation Research Programme C01X1002. Special thanks to Tracey Burton and Elsemieke Kin for field assistance. www.niwa.co.nz