Productivity, nutrient input, nutrient uptake, and release rates were determined for a coral-dominated reef flat at La Réunion, France, to assess the influence of groundwater nitrogen on carbon and nutrient budgets. Water samples were collected offshore in the ocean, at the reef crest and back reef for nutrients, picoplankton, pH, and total alkalinity. Volume transport of ocean water across the reef flat was measured using both current meters and drogues. Groundwater advected onto the reef flat and mixed with incoming ocean water. Metabolic rates for the reef community were determined to be: gross primary production = 1,000 mmol C m−2 d−1, community respiration = 960 mmol C m−2 d−1, and community calcification = 210 mmol C m−2 d−1. Across the reef flat, silicate behaved conservatively, there was net uptake of phosphate (0.06 mmol P m−2 d−1) and net release of nitrate, ammonia, dissolved and particulate organic nitrogen (total 7.0 mmol N m−2 d−1). Groundwater nitrate contributed 37% of the increase in nitrate plus ammonia. The first-order mass transfer coefficient of phosphate was 3.3 m d−1, and for nitrate plus ammonia, 5.9 m d−1. Gross N and P uptake from estimates of mass transfer and uptake of particles were 0.37 mmol P m−2 d−1 and 7.2 mmol N m−2 d−1, respectively giving an N:P uptake ratio of 20:1. Thus, the elevation of nitrogen across the reef flat maintains a high N:P flux, enhancing algal growth downstream of the transect. We conclude that net community production (40 mmol C m−2 d−1) was sustained by net uptake of phosphate from the ocean and net uptake of new nitrogen from groundwater

No abstract

No . 5 9 6 P AR T 1 : L o n g -T e r m Mo n i t o r i n g o f T wo S h a l l o w Co r a l Re e f Co mmu n i t i e s C a t h e r i n e T o u r r a n d , Od i l e N a i m, L i o n e l B i g o t , C h r i s t o p h e C a d e t , B r u c e C a u v i n , S t u a r t S e mp l e , L u c i e n F . Mo n t a g g i o n i , P a s c a l e C h a b a n e t a n d He n r i c h B r u g g e ma n nNo . 5 9 7 No . 5 9 7 P AR T 2 : L o n g -T e r m Mo n i t o r i n g o f P r i ma r y P r o d u c e r s Od i l e N a i m, C a t h e r i n e T o u r r a n d , E n r i c B a l l e s t e r o s , S t u a r t S e mp l e , L i o n e l B i g o t , B r u c e C a u v i n , P a s c a l e C u e t , a n d L u c i e n F . Mo n t a g g i o n i No . 5 9 8 P AR T 3 : L o n g -T e r m Mo n i t o r i n g o f L i v i n g Co r a l s Od i l e N a i m, C a t h e r i n e T o u r r a n d , Ge r a r d F . F a u r e , L i o n e l B i g o t , B r u c e C a u v i n , S t u a r t S e mp l e a n d L u c i e n F . Mo n t a g g i o n iA T OL L R E S E AR C H B UL L E T I N NOS . 5 9 6 -5 9 8 FRINGING REEFS OF REUNION ISLAND AND EUTROPHICATION EFFECTS ABSTRACTThis study assesses changes in subtidal benthic communities on the largest reef flat in Reunion, Saint-Gilles La Saline, using several types of surveys. Temporal and spatial trends are documented over a 22 year period , thus spanning the 1998 and 2000s bleaching events. The most plausible explanations for the observed trends are proposed. We chose two sites that are characterized by two types of community and metabolism: (1) an oligotrophic site dominated by Acropora corals (Site-Toboggan), where sea-urchins are numerous and macroalgae rare and (2) a dystrophic site dominated by non-Acropora corals, mostly massive and submassive, where macroalgae abound and sea-urchins are almost absent (Site-Planch'Alizés). Results are presented in three parts : Part 1 : general trends of the communities, part 2 : primary producers, part 3 : living corals.Part 1 presents three surveys. Survey 1 reports status and trends across the reef flats in 1993, 1996, and 2002, with all attached benthic components reported at the level of the species where possible. Survey 2 reports composition and changes in associated sedentary organisms such as sea urchins, holothurids, and the Pomacentridae fish Stegastes. Survey 3 focuses on the period 1998 to 2009 on permanent transects established in 1987 and monitored periodically, partly as a contribution to the Global Coral Reef Monitoring Network (GCRMN). In general, community structures at both locations remained stable, with primary producer coverage around 5% at Toboggan (T) and around 60% at Planch'Alizés (P). Living coral coverage averaged around 17% at both sites, but it was dominated by Acropora on Site-T (68%) and by massive corals on Site-P (88%). Regular echinoids were very abundant at T but almost absent from P, while the opposite was true for holothurids. The territorial damselfish Stegastes was of comparable abundance at both sites (<1 individuals per m 2 ). There were large changes in...

No . 5 9 6 P AR T 1 : L o n g -T e r m Mo n i t o r i n g o f T wo S h a l l o w Co r a l Re e f Co mmu n i t i e s C a t h e r i n e T o u r r a n d , Od i l e N a i m, L i o n e l B i g o t , C h r i s t o p h e C a d e t , B r u c e C a u v i n , S t u a r t S e mp l e , L u c i e n F . Mo n t a g g i o n i , P a s c a l e C h a b a n e t a n d He n r i c h B r u g g e ma n nNo . 5 9 7 No . 5 9 7 P AR T 2 : L o n g -T e r m Mo n i t o r i n g o f P r i ma r y P r o d u c e r s Od i l e N a i m, C a t h e r i n e T o u r r a n d , E n r i c B a l l e s t e r o s , S t u a r t S e mp l e , L i o n e l B i g o t , B r u c e C a u v i n , P a s c a l e C u e t , a n d L u c i e n F . Mo n t a g g i o n i No . 5 9 8 P AR T 3 : L o n g -T e r m Mo n i t o r i n g o f L i v i n g Co r a l s Od i l e N a i m, C a t h e r i n e T o u r r a n d , Ge r a r d F . F a u r e , L i o n e l B i g o t , B r u c e C a u v i n , S t u a r t S e mp l e a n d L u c i e n F . Mo n t a g g i o n iA T OL L R E S E AR C H B UL L E T I N NOS . 5 9 6 -5 9 8 FRINGING REEFS OF REUNION ISLAND AND EUTROPHICATION EFFECTS ABSTRACTStudies on the reef flat of Saint-Gilles La Saline between 1987 and 2009 compared spatio-temporal variations of primary producers on two sites, Toboggan and Planch'Alizés. Toboggan (Site-T) is an oligotrophic site characterized by Acropora corals, abundant sea urchins and few primary producers. Planch'Alizés (Site-P) is a heterotrophic site, characterized by massive corals, abundant primary producers and occasional sea urchins. From shore to outer reef front, the reef flat comprises three parts: the back reef (B), the coral zone with Large coral strips (L) and the coral zone with Narrow coral strips (N). This paper (which is Part 2 in a three part series) is divided into four sections. The first (1993, 1996, and 2002) focuses on four groups of primary producers: cyanophytes; turfs (including Stegastes epilithic algal communities); encrusting coralline algae; macroalgae. Their abundance and dominant species were recorded in the three subzones, B, L and N, using 50m-line intercept transects (LITs). The second section (1998 to 2009 inclusive, on the two same sites), reports on annually monitored turfs, encrusting coralline and macroalgae on two permanent 20m LITs. These annual records extend periodic records from these same LITs from 1987LITs from , 1993LITs from , 1996LITs from and 2002. The third section describes species richness of primary producers at the infracentimetric level in zones B, L and N in 1994. In the final section, seasonal variability is documented as changes in the biomass of dominant macroalgae reported monthly over a period of seven months (1993-94).In 1993-2002, primary producers were dominant at P (average ~ 60%) but inconspicuous at T (~5%). In terms of relative cover, turfs and macroalgae were the dominant forms at both sites (75% turfs, 10% macroalgae at T ; 24% t. and 52% m. at P). On both sites, cyanophytes significantly decreased over time. Among turfs, fine filamentous turfs were pr...

No . 5 9 6 P AR T 1 : L o n g -T e r m Mo n i t o r i n g o f T wo S h a l l o w Co r a l Re e f Co mmu n i t i e s C a t h e r i n e T o u r r a n d , Od i l e N a i m, L i o n e l B i g o t , C h r i s t o p h e C a d e t , B r u c e C a u v i n , S t u a r t S e mp l e , L u c i e n F . Mo n t a g g i o n i , P a s c a l e C h a b a n e t a n d He n r i c h B r u g g e ma n nNo . 5 9 7 No . 5 9 7 P AR T 2 : L o n g -T e r m Mo n i t o r i n g o f P r i ma r y P r o d u c e r s Od i l e N a i m, C a t h e r i n e T o u r r a n d , E n r i c B a l l e s t e r o s , S t u a r t S e mp l e , L i o n e l B i g o t , B r u c e C a u v i n , P a s c a l e C u e t , a n d L u c i e n F . Mo n t a g g i o n i No . 5 9 8 P AR T 3 : L o n g -T e r m Mo n i t o r i n g o f L i v i n g Co r a l s Od i l e N a i m, C a t h e r i n e T o u r r a n d , Ge r a r d F . F a u r e , L i o n e l B i g o t , B r u c e C a u v i n , S t u a r t S e mp l e a n d L u c i e n F . Mo n t a g g i o n iA T OL L R E S E AR C H B UL L E T I N NOS . 5 9 6 -5 9 8 FRINGING REEFS OF REUNION ISLAND AND EUTROPHICATION EFFECTS ABSTRACTSpatio-temporal variations of living coral coverage, species richness and diversity were studied on two fringing reef sites at Saint-Gilles La Saline on Reunion Island from 1987 to 2009. The Site-Toboggan (T) was characterized by oligotrophy, Acropora corals, abundant sea urchins and few primary producers. The SitePlanch'Alizés (P), was characterized by heterotrophy, massive corals, abundant primary producers and rare sea urchins. From the shore to the outer reef slope, both reef flats comprise the back reef at around 1.5m deep ('B'), coral zone 'L' with large shore-normal strips of coral 0.8m deep, coral zone 'N' with narrow shore-normal strips of corals at around 0.4m deep, and an outer reef flat (<0.4m deep, with breaking surf -not studied). In the period 1993 to 2002, a total of 36 coral species was recorded (31 species at T, 19 at P). In 1993, after a 1992-bleaching event, Acropora coverage was low and only 3 species were recorded (A. muricata, A. cytherea, A. abrotanoides). By contrast, in 2002, when Acropora cover was much higher, there were 11 species, but only two at P in the 1993-2002 interval. The highest coral diversity (Shannon index, H') occurred on the N coral zone at T in 1996, following an increase from 1993, and after which it declined, as the staghorn coral A. muricata strongly increased its cover. By comparison, non-Acropora coverage remained relatively stable at T. At P, coral coverage increased from 1993 to 2002 in both coral zones but only the increase of Porites (Synaraea) rus was statistically significant. Overall, trends in coral cover and diversity indicate both sites were in better health in . Between 1987 The number of coral species on the reef flats may have slightly decreased in the last 40 years. Faure ( , 2009) recorded 74 species in the1970s and 71 species in 2009, of which 36 species were recorded on inner reef flats and 62 species on outer reef flats. The number of species reco...