Rainfall influence upon nutrient inputs to Caribbean coastal systems. Tim Carruthers

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1 Rainfall influence upon nutrient inputs to Caribbean coastal systems Tim Carruthers

2 Outline Thalassia as an indicator for the Caribbean Use of δ 15 N Nutrient sources to a dry Caribbean Lagoon, Yucatan Mexico Nutrient sources to a wet Caribbean Lagoon, Bocas del Toro, Panama Comparison and conclusions

3 Thalassia testudinum grows in bay, lagoon and reef habitats Thalassia grows near rivermouths in fine mud Thalassia grows in high light Thalassia grows amongst Porites reef in very coarse carbonate sediment maximum depth limit of Thalassia is ca 14% SI

4 Global distribution of Thalassia T. hemprichii T. testudinum Courtesy Michelle Waycott

5 Thalassia testudinum (Caribbean) genetically distinct from Thalassia hemprichii (Indo Pacific) Courtesy Michelle Waycott

6 Thalassia has long distance (2700 km) vegetative dispersal Photo: Bill Dennison Thalassia testudinum Bermuda Thalassia testudinum San Blas, Panama A single genetic individual was collected in both San Blas (Panama) and Bermuda Courtesy Michelle Waycott

7 Thalassia is relatively long lived with slow turnover therefore a good integrator Courtesy: Bill Dennison

8 Thalassia testudinum is an ideal sentinel species for the Caribbean Wide dispersal suggests Caribbean is one potentially interbreeding population Within systems, T. testudinum grows from river mouth to reef T. testudinum is a relatively long lived, slow turnover species providing an integrated sample in time T. testudinum is abundant

9 Method for analysis of δ 15 N Collect sample Dry and grind Analyse on Mass spectrometer ( At%15N At%15N ) sample standard At%14N At%14N δ 15 N (%o) = x 1000 At%15N standard At%14N

10 Unenriched N source 15 N 0.4% 14 N 99.6% Atmosphere (N 2 ) Rain (630 µg L -1 N) Fixed by Cyanobacteria etc Metabolized N source 15 N 0.4% 14 N 99.6% Within plant/algae/phytoplankton Consumption 15 N 0.4% 14 N 99.6% Digestion & excretion 15 N 0.4% 14 N 99.6% Eg marine δ 15 N= 0 15 N 0.405% 14 N % Eg marine δ 15 N= 12.5

11 Nichupte and Puerto Morelos Lagoons are in the north east Caribbean Yucatan peninsula (Mexico) Nichupte and Puerto Morelos Lagoons Photo: NASA

12 Nichupte and Puerto Morelos Lagoons have groundwater inflow Sink holes Cenotes are common throughout the Yucatan Intense hotel development has occurred and is expanding

13 Intense and rapid hotel development has occurred in past two decades

14 North west Caribbean has m annual rainfall with no clear wet and dry Total Monthly (mm) Mean annual rainfall mm Data from Brigit van Tussenbroek

15 T. testudinum has higher %N in Nichupte Lagoon than in Puerto Morelos Lagoon %C %N %P C:N:P a :42: ab :50: bc :26: c :32:1 p= 0.28 < Nichupte Lagoon north Nichupte Lagoon south Puerto Morelos springs Puerto Morelos Lagoon Flushing in Nichupte north is 1.9 yrs Two narrow openings to Nichupte Lagoons

16 T. testudinum %N in Nichupte Lagoon has increased in last 10 yrs 1991 (mean se ) 2002 (mean se ) %C %N %P C:N:P 680:32:1 749:51:1 C:N 21:1 15:1

17 Sewage is the source of increasing nitrogen in Nichupte Lagoon %N δ 15 N a a a 541:42: ab ab ab 794:50: bc bc :26: c c c 740:32:1 p= <0.1 <0.1 Nichupte Lagoon north Nichupte Lagoon south Puerto Morelos springs Puerto Morelos Lagoon

18 During rain events, T. testudinum near submarine springs has increased %P Nutrient source Increased %P in seagrass tissue implies that either phosphorus or iron is entering Puerto Morelos Reef Lagoon through submarine springs Location season %C %N %P C:N:P n Submarine springs dry :26:1 4 Submarine springs rain :11:1 3 Lagoon dry :32:1 6 Lagoon rain :31:1 20 Fe Fe

19 Nutrient inputs to the west Yucatan Peninsula Fe Fe

20 Bocas del Toro is in the south west Caribbean Photo: NASA Panama Bocas del Toro

21 South west Caribbean has 3-6m annual rain with two mini dry seasons Monthly Total Bocas del Toro rainfall (mm) Yucatan rainfall Lower rainfall in Feb/March & Sept/Oct extended dry 2003 Mean annual rainfall (-6000) mm Data provided by Karl Kauffman

22 Bocas del Toro has high sediment and nutrient watershed inputs Land clearing for wood Sewage inputs Slumping and hillslope erosion Riverbank erosion, banana plantations

23 T. testudinum %P high throughout Bocas archipelago, highest in the north Bay 0.26% ±0.01 Reef 0.27% ±0.02 Global : median 0.18% Duarte % ±0.01 Florida Bay: median 0.11% Fourqurean and Zieman 2002 Lagoon Thalassia testudinum leaf %P

24 T. testudinum %N high throughout Bocas del Toro archipelago Bay 2.46% ±0.08 Reef 2.46% ± % ±0.13 Global : median 1.8% Duarte 1990 Florida Bay: median 1.76% Fourqurean and Zieman 2002 Lagoon Thalassia testudinum leaf %N

25 Thalassia testudinum tissue nutrients Global Florida Seagrass Bay median median Bay Lagoon Reef C:N 20:1 24:1 15:1 15:1 16:1 C:P 435:1 874:1 312:1 364:1 338:1 N:P 22:1 36:1 20:1 24:1 21:1

26 High nutrient inputs from watershed throughout Bocas del Toro archipelago

27 Some Lagoons in both Yucatan and Bocas del Toro show nutrient status which is globally high. %N %P C:N:P Sewage (Nichupte) :42:1 Pristine (PM Lagoon) :32:1 Bocas :22:1 Global :22:1 Florida Bay :36:1

28 Conclusions Thalassia is an effective bio-indicator for the Caribbean Use of δ 15 N clarified anthropogenic influences to both high and low rainfall Caribbean systems A dry Caribbean Lagoon, Yucatan shows high sewage nitrogen inputs and high phosphorus inputs from submarine vents A wet Caribbean Lagoon, Bocas del Toro shows high total nitrogen and phosphorus inputs from watershed sources

29 Recommend watershed management in Bocas del Toro to reduce erosion and fertilizer inputs. Recognition of the extent of impact of riverine inputs is required. Recommendations Thalassia testudinum is a sentinel species, recommend a Caribbean wide database and to assess more locations. Recommend both broad scale and local assessments of δ 15 N to aid in determining nitrogen sources. Recommend management of west Yukatan hotel development, specifically sewage treatment.

30 Acknowledgements Yucatan: Brigit van Tussenbroek Bill Dennison field Kor Jent, Daniel Flores, Fransisco Renteria UNAM Panama: Penny Barnes Jim Fourqurean field Gabriel Jacome, Victoria Collins, Maricella Salazar, Willy Pomares, Arcardio Castillo, David Kline, Jane Thomas FIU

31 For more information: IAN (Integration Application Network)