Interactive comment on “ Influences of tidal energy advection on the surface energy balance in a mangrove forest

Introduction Conclusions References


Introduction
Despite their ecological importance, coastal ecosystems remain largely under-studied for their capacity to store carbon and cycle energy.For example, the fringe mangrove forests in the Florida Everglades provide a wide range of ecosystem services for local fisheries (Odum and Heald, 1972;Odum et al., 1982) and atmospheric carbon dioxide assimilation (Barr et al., 2010(Barr et al., , 2012)).Their pan-tropical distribution and continuous growing season permit mangrove forests to exhibit unique carbon and energy cycling patterns (Barr et al., 2010).To fully understand and quantify forest-atmosphere carbon and water vapor exchanges, it is necessary to ascertain the mechanisms and time scales of energy flows through forested systems (Wilson et al., 2002).In mangrove forests, the flow of water during flood and ebb tides may substantially influence the energy transport within the canopy.In terrestrial ecosystems, available energy represents the difference between net radiation (R net ) and the flux of heat into or out of the soil (G).Neglecting energy stored in the biomass, the available energy (R net − G) is then partitioned into sensible (H) and latent heating (LE) in the vertical direction.In tidal settings, water inundating the forest floor stores or releases energy as well as carries energy to and from adjacent estuaries.The energy exchange that occurs during flood and ebb tidal cycles must be incorporated into the surface energy budget.
Limited studies have attempted to quantify energy flows in coastal landscapes affected by variable surface water levels.Heilman et al. (1999Heilman et al. ( , 2000) ) used conditional eddy-covariance and Bowen ratio methods to determine the components of the surface energy balance of a coastal marsh near Corpus Christi, TX.Their results showed a poor closure of the surface energy balance that depended on surface water levels and exhibited a strong seasonal signal.Annual energy fluxes revealed that the marsh functioned more like a dryland ecosystem, with enhanced latent heat prevailing in the spring during the highest water levels and greatest sensible heat in the summer.In the coastal environment, a clear relationship existed between surface water levels and energy flows.Also, Hoguane et al. (1999)  equations to estimate temperature and salt dynamics of the Ponta Rasa mangrove swamp in Mozambique.The Ponta Rasa system, which exhibited a twice-daily tide component, was divided into two reservoirs: the Maputo Bay and the mangrove swamp.
Results indicated that heat and salt were laterally transported in narrow channels connecting the reservoirs.
In the tidally influenced mangrove forests of the Everglades, FL, USA estuarine waterways flow southwest to the Gulf of Mexico and flood the forest floor up to two times a day (Fig. 1).During low tides in the summer, the water is cooler than the overlying air in the afternoon, and the receding water transports heat away from the forest floor to the adjacent estuary.The physical process of heat transfer occurs as the cool water contacts warmer soils below and air above during flood tide periods.During these periods most of the energy exchange occurs across the soil-water and water-atmosphere interfaces at points of water entry into the mangrove forest (the mangrove-estuary interface) and along the sediment-water and water-atmosphere interfaces as the tidal waters penetrate into the forest.These unique energy exchange processes have not been previously explored in coastal systems.It is necessary to understand these energy flows because their temporal variability has implications for fluctuations in soil and air temperature, which influence net ecosystem carbon exchange (NEE) over daily and annual time scales (Barr et al., 2012;Ito et al., 2005;van Dijk et al., 2005).
This study aimed to determine the heat flux into the water inundating the soil surface to improve energy budgets for the tidally influenced mangrove forest by accounting for both (i) lateral advection of energy at the forest-estuary interface and (ii) vertical exchanges of energy at the water-soil and water-atmosphere interfaces.We estimated the vertical transport of energy at the forest-atmosphere interface and the lateral ad and the consequential influences on physiological processes including photosynthesis and water use efficiency.

Site description
Located mostly within the boundaries of Everglades National Park (ENP), mangroves represent the dominant primary producers within the coastal Florida Everglades and extend over 1.75 × 10 7 ha (Lugo et al., 1975).The ENP includes over 4.3 × 10 5 ha of the Everglades watershed, which is one of the largest freshwater wetland landscapes in North America.The study site was located within a riverine mangrove forest along Shark River (Fig. 1), adjacent to the Florida  of Shark River.An eddy covariance system was used to calculate fluxes of sensible (H) and latent (LE) heat transported across the forest-atmosphere interface (Fig. 2).Vertical wind velocity and temperature were measured at 10 Hz with a 3-dimensional sonic anemometer (model RS-50, Gill Co., Lymington, England) mounted at 27 m.An adjacent open path infrared gas analyzer (Li-7500, LI-COR Inc., Lincoln, NE) measured water vapor concentration at 10 Hz.These measurements were processed with custom-made software to derive half-hourly fluxes of H, LE, carbon dioxide (CO 2 ), and momentum exchanges between the forest and overlying atmosphere (Barr et al., 2010).Software data processing includes spike removal (Vickers and Mahrt, 1997), buoyancy corrections of sonic air temperatures (Schotanus et al., 1983), and calculation of the total constituent flux (Webb et al., 1980) which accounts for positive vertical mass flow resulting from buoyancy of less dense air parcels.Relative humidity at 27 m was calculated with measurements from a ventilated thermistor-hygristor probe.
A net radiometer (Model CNR 1, Kipp and Zonen, Bohemia, NY) recorded net radiation (R net ).Heat flux plates (model HFT 3.1, Campbell Scientific, Logan, UT) were placed at 0.1 m below the sediment surface measured the direction and magnitude of energy flow (G) through the soil.In terrestrial ecosystems, the soil serves as a capacitor for heat, whereby heat is stored during the daytime and released to the atmosphere during the nighttime.However, in mangrove ecosystems, the lateral advection of enthalpy (∆H adv ) describes the amount of energy stored (or released) from the water column and exchanged with the estuary during flood and ebb tides.The magnitude of ∆H adv is controlled by four distinct processes: (i) heat transfer (conduction) between the sediment and overlying water column, (ii) heat conduction between the water column and the overlying atmosphere, (iii) evaporation at the water-atmosphere interface (removing heat from the water column), and (iv) direct absorption of solar irradiance by the water column.During ebb tides, enthalpy is transferred from the water inundating the surface into the surrounding estuary, which is outside of the tower flux footprint contributing to H and LE (Fig. 2).The surface energy balance can then defined as

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Full where S includes energy required to heat (or cool) above ground biomass and air between the surface and 27 m and chemical energy stored during photosynthesis (Gu et al., 2007).A positive value of S indicates storage of energy within the ecosystem during the time interval (30 min) and contributes to lowering of the energy available for partitioning into sinks.The magnitude of S can be important (∼ 5 % of R net ) during short (30 min) time intervals.However, when components of the energy budget are integrated over time periods of a day or more, S is generally negligible (< 5 % of R net ) compared to the other source and sink terms.This simplification provides the energy budget used in this study (Fig. 2), Closure of the surface energy budget was determined as the slope of the least-squares regression line forced through the origin of daytime half-hourly available energy (R net − G) versus energy sink terms in Eq. ( 2) during the 10-day study period.The analysis was performed separately by both including and excluding ∆H adv as one of the sink terms along with H and LE.To account for the possibility that the time scales of energy sinks were not exactly synchronized with available energy input, cumulative daytime fluxes of (R net − G), (H + LE) and (H + LE + ∆H adv ) in MJ m −2 were determined.Energy closure was estimated as the ratio of the cumulative energy sink, with and without ∆H adv included, to cumulative available energy at the end of the study period.

Estimation of lateral energy fluxes
We quantified lateral energy advection by tides at the study site (Fig. 1) by considering mass and energy budgets for water similar to Hoguane et al. (1999).To obtain spatially accurate temperature and water level gradients, the study site was partitioned into four rectangular sectors, A through D (Fig. 3).Three independently instrumented locations (Sites 1-3; Fig. 3) were established along a transect extending from the edge of Shark River to the flux tower (∼ 250 m).As in previous studies (Heilman et al., 2000), heat fluxes into or out of the soil were determined at each site using heat flux plates (model Introduction

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Full The ∆H stor (W m −2 ) is the difference in enthalpy storage between the current period (H stor,i ) and the previous one (H stor,i −1 ) during the time interval, ∆t.At each time step, H stor was determined as, where ρ is the density of water (kg m −3 ) and C w is the specific heat capacity of water ).The h j , A j , and T j are water depth (m), area (m 2 ), and average water temperature (C), respectively, within each sector j .The total drainage area of the tidal creek (A tot = n j =1 A j ) was determined from linear least-squares regression of the flow entering (exiting) the tidal creek during each 10 min interval versus the change in the sum of cross sectional area of water inundating the surface in all four sectors.During flood and ebb tide periods, when the soil was inundated, the slope of the regression provided an estimate of the width (w) of the creek drainage perpendicular to the creek axis and the line connecting the 3 sites and tower.This width was then used to estimate the rectangular area of each sector (Fig. 3) and the change in volume resulting from flow through the tidal creek.During tidal inflows (outflows), the enthalpy entering (exiting) the forest through the tidal creek was estimated as, where ∆V (m 3 ) is the total volume change during time interval, ∆t (s), in all four sectors, and T cr (C) is the average water temperature entering (exiting) the mouth of the tidal creek.During ebb tide (∆V < 0), and energy is exiting the forest (H in < 0 in Eq. 6).Introduction

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Full During the end of ebb tide, the water level in the creek dropped below 0.05 m and the enthalpy exported to the estuary was estimated as, where ∆V j (m 3 ) is the change in volume within each sector.During these periods, water inundating the surface was also likely exported through seepage in the sediment, overbank flow, and flow through the tidal creek.Any additional heat transfer that may have occurred as the water flowed through the sediment and into the tidal creek or river banks was not measured and was therefore not included in this analysis.However, when water levels were high (> 0.05 m above the surface) the flow through tidal creeks was the primary mechanism for export of water and enthalpy into the adjacent river.
Recharge was not used in determining import and export of enthalpy since the analysis required mass balance closure.

Radiation loads and energy partitioning
Limited information exists on long-term (> months) sensible and latent heat fluxes for tidally influenced mangroves.To determine whether forest-atmosphere energy changes exhibit different patterns during high and low tides, averaged fluxes were estimated for seasonal periods similar to the ones included in the 10-day study.During July to September 2004 and July and August 2005, average midday (12:00-14:00 h) R net (Fig. 4a) was higher during low tide periods (535-640 W m H and LE were mostly controlled by R net , the partitioning of energy into H and LE was weakly controlled by tidal inundation status.Diurnal average H / R net and LE / R net ratios (data not shown) were 7 % to 13 % and −4 % to 15 % higher, respectively, comparing low to high tides during 12:00 to 15:00 h.Soil heat flux adjacent to the tower (Fig. 4d) was ∼ 5 W m −2 higher comparing low to high tides during 13:00 to 15:00 h.During daytime hours, the soil was a weak source of energy (−7 to 2 W m −2 , on average) in the morning (07:00 to 10:00 h) and a weak sink of energy (2 to 16 W m −2 , on average) during the afternoon (12:00 to 18:00 h), regardless of inundation.These results suggest that tidal flows provided an additional sink of energy during the warm summer months of July to September.

Water flow dynamics and tidal energy advection
Although topographic changes in the mangrove forest landscape were slight (1 m or less), the differences strongly affected the flow dynamics at the study site.Flow dynamics are illustrated by the time series of water level on the forest floor at three sites (Fig. 5a) and within the tidal creek (Fig. 5b).Tidal fluctuations were highly asymmetrical during incoming and outgoing tide.During flood tide, water levels increased rapidly as water was forced through the tidal creek.However, during ebb tide, the flow of water was resisted by soil roughness, the presence of pneumatophores, and obstacles such as coarse woody debris and leaf litter.This reduction in flow was most evident in the inflection in water levels at sites 2 and 3 that occurred as levels dropped below about 0.1 m.Within these ebb tide periods, a fraction of water percolated through the soil and returned to the river through lateral subsurface flow rather than exiting directly through the tidal creek.Subsurface flow was also evidenced by asymmetric recharge through the tidal creek (Fig. 5c).Flow entering through the creek (i.e., recharge) was visible during each flood tide, but discharge of water exiting the creek during ebb tides was substantially dampened and in some cases not observed.The width of the creek Introduction

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Full drainage was estimated as 340 m as determined from the slope of the regression line of flow through the creek versus change in cross sectional area in the four sectors.This large (340 m) drainage width provided some context for the asymmetry in creek discharge observed during ebb tide periods.The timing of tidal flows and inundation (Fig. 5) in relation to available energy represented a key control on the direction and magnitude of tidal energy advection.On 13 August 2005, floodwaters were initially a source of energy to the forest in the morning (∆H adv = −165 W m −2 at 08:30 h; Fig. 6a) when inundation was greatest (Fig. 6b).
During ebb tides, when water drained from the forest floor (09:30 to 13:30 h), the receding waters were a sink for available energy (up to 320 W m −2 ).Higher air temperature and positive available energy (not shown) resulted in air-water heat transfer and direct warming of the water column from absorption of solar irradiance.Diurnal patterns in H and LE on 13 August (Fig. 6a) were representative of energy exchange rates observed during the 10-day study period.Daytime LE exceeded H by a ratio of roughly 2 : 1. Temporal patterns in soil heat flux were comparable at the tower and averaged for the 3 sites (G tower, Fig. 6a).The soil served as a weak sink for energy (G of 5-17 W m −2 ) during the daytime and a weak source of energy (G of −10 to 0 W m −2 ) during nighttime hours.
Ensemble averages of energy source and sink terms (Fig. 7) were used to understand the role of tidal energy advection in the surface energy budget during the 10day study period when the forest was flooded.The R net (Fig. 7a) was highest (580-810 W m −2 ) during 12:30 h coincident with peak solar irradiance levels (not shown).
Both H and LE (Fig. 7b and c This shift in average ∆H adv during the afternoon from a sink to a source of energy mostly drove the secondary peaks in H and LE.Soil heat flux trends played a minor role compared to ∆H adv in controlling diurnal energy partitioning into H and LE with maximum values of 11-18 W m −2 (average ±1 s.d.) at 13:30 h.Though diurnally variable, tidal energy advection provided a net sink for energy during the 10-day study period.However, the sign and the magnitude of ∆H adv over the course of seasonal cycles likely varied with changes in the temperature gradients between the atmosphere and the floodwaters entering from the river.Least squares regression (Fig. 8) of half-hourly daytime ∆H adv versus the difference between air temperature (at 27 m) and water temperature (site-and depth-averaged) showed a significant increase (p < 0.01) in ∆H adv with increasing temperature gradient (slope = 44.7,intercept = −1.4,R 2 = 0.25).This trend indicated that flood tides changed from being a net sink to a net source of energy during seasonal transitions in October-November when air masses in south Florida begin to cool but waters in the Gulf of Mexico remain warm.Also, cold fronts lasting for several days frequent the Everglades during December to March.During these periods, floodwaters from Shark River can be warmer than midday conditions and provide a source of heat to the forest.Tidal waters may, therefore, serve to ameliorate extreme microclimatic conditions (associated with extreme heating during the summer or unusual coldness during the winter) within the forest canopy.Extreme microclimatic conditions detrimentally impact leaf physiology and net ecosystem carbon exchange (Barr et al., 2010).
Including the energy transfer associated with tidal activity improved the closure of the surface energy balance in the mangrove forest during 6-16 August 2005.When the ∆H adv was considered in the surface energy budget, energy closure improved from 73 % to 82 % (Fig. 9a and b, respectively).Therefore, tidally driven floodwaters represented a net sink of energy during the daytime.The regressions between available energy and energy sinks (Fig. 9 midday (12:00 to 14:00 h).Closure was highest (82-88 %) during the morning (09:00 to 10:00 h) and late afternoon (15:30 to 17:00 h), when R net and solar irradiance were lower compared to midday levels.To remove any effect these patterns may have had on energy closure, the energy budget was also determined from daytime cumulative sums of energy input (R net − G) and output (Fig. 10) that did not and did include tidal energy advection ([H + LE] and [H + LE + ∆H adv ], respectively).At the end of the study, cumulative sums of (H + LE) and (H + LE + ∆H adv ) represented 79 % and 91 % of available energy, respectively (Fig. 10).The cumulative summation method provided the evidence of improved energy closure (79 % and 91 %).Furthermore, regression analyses yielded differences (73 % and 82 %) in the degree of surface energy closure whether ∆H adv was included or excluded as energy sink.The inclusion of ∆H adv as an energy sink improved closure by 9 to 12 %.Therefore, advection of energy by tides should not be ignored for its contribution to surface energy budgets in mangrove forests.
The results for the surface energy balance were consistent with previous findings that showed a lack of energy budget closure of about 20 % for various terrestrial ecosystems (Wilson et al., 2002).Even with the contribution of ∆H adv , the energy budget failed to close based on the regression and cumulative sum methods by 18 % and 9 %, respectively.In the present study, the "missing" energy likely originated from both underestimating sensible and latent heat fluxes (Sakai et al., 2001) and not accounting for heat storage in biomass and biochemical reactions (Gu et al., 2007).The present analysis quantified energy transport occurring in surface waters, which included water inundating the soil surface, flow through the tidal creek, and loss in volume through overland flow.Some net loss of energy likely resulted from subsurface flow and heat exchange with the soil.This subsurface flow did not entirely leave the tidal creeks, but some seeped through interstitial spaces along the steep soil banks lining the adjacent river.In a temperate deciduous forest, Gu et al. (2007) found that biomass heat storage and biochemical energy storage ranged from −50 to 50 W m

Conclusions
Results from the present study showed that energy advection associated with tides in a mangrove forest meaningfully affect the surface energy budget.For the warm periods experiencing high (∼ 800 W m −2 ) net radiation loads, flooding waters provided a net sink for energy.During high tides, the cooler water inundated the warmer soils and, during low tides, the dissipated heat in the water column resting on soils was transported to the adjacent river.For the duration of the study period, the average energy advection rates ranged from −273 to 291 W m −2 (5th to 95th percentiles).Such energy fluxes substantially exceeded soil heat fluxes whose values ranged from −20 to 27 W m −2 (5th to 95th percentile).When the lateral transport of energy was included in the surface energy balance then the closure of the energy budget improved by 9 % to 12 %.The positive correlation observed between lateral energy transport and air-water temperature differences indicated that flood tides provided a microclimate buffer in the mangrove forest ecosystem.Results suggest that during seasonal transitions to cooler air masses, routinely experienced in the Everglades in October and November, warm waters from the Gulf of Mexico provide a net source of energy (when water temperature exceeds air temperature).In this manner, the tidal flows serves as a conduit to transport energy between mangrove forests and coastal waters.
utilized conservation of mass and heat flow Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | vection of energy by computing the temporal changes in enthalpy of floodwaters during residence within the flux footprint of an eddy covariance (EC) tower.Results were used to understand the mechanics of tidal energy flows and the magnitude of these in relation to vertical exchanges of latent and sensible heat.This work represents a first step toward understanding how tidal energy exchange affects the mangrove microclimate Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |HFT 3.1 Heat Flux Plates, Campbell Scientific Inc., Logan, UT) buried 0.1 m below the sediment surface.Spatially averaged soil heat flux including the 3 sites was used to represent G in Eq. (2) in place of the measurements adjacent to the tower.Measurements included periods when the soil was exposed and inundated during flood tides.At each site, water temperature was measured with three type E thermocouples (Omega Engineering, Inc., Stamford, CT) deployed at different heights (0.05, 0.13, and 0.31 m) above the soil surface.A water level sensor (model WL400, Global Water Instrumentation, Inc., Gold River, CA) provided water depth at each site, which was used to identify periods when thermocouples were exposed to the atmosphere.Within the mouth of the tidal creek, E-type thermocouples were also deployed at 0.05, 0.13, and 0.31, and 0.51 m.Flow velocity in the creek was measured with a flow meter (model Flo-Tote 3, Marsh McBirney, Frederick, MD).Point measurements of velocity were converted to depth-and width-averaged velocity (U; in m s −1 ).Water level, measured by the flow meter's pressure transducer, along with user specified information of the channel geometry, was used to compute instantaneous cross-sectional area, A (in m 2 ).Recharge quantities (Q; in m 3 min −1 ) entering (exiting) the tidal creek from Shark River was determined as 10-min averages asQ = 600 s t=0 (UA)dt 10 min(3)Water temperature (T i ) in sectors A-D (Fig.3) were determined by assuming a linear temperature gradient between each site and solving for the temperature at the midpoint of each sector along a transect connecting the sites.Water temperatures were vertically and temporally averaged at each site and included only those measurements when thermocouples were submerged.The ∆H adv (W m −2 ) was determined as the change in enthalpy storage (∆H stor ) of water inundating the surface and contributions from flow entering (H in > 0) or exiting (H in < 0) the forest via the adjacent river divided by the time interval, ∆t (i.e., 10 min (600 s)) over which the change occurred.∆H adv = (∆H stor − H in ) /∆t (4Discussion Paper | Discussion Paper | Discussion Paper | Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | −2 ) compared to high (525-560 W m −2 ) tide periods.These trends contributed to increased midday H (Fig. 4b) during high (H of 150-180 W m −2 ) compared to low tide (H of 125-140 W m −2 ) periods.Average midday LE (Fig. 4c) was also higher during low (LE of 250-315 W m −2 Discussion Paper | Discussion Paper | Discussion Paper | compared to high tide (LE of 225-265 W m −2 ) periods.While the magnitudes of midday Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) peaked prior to the maximum R net at 11:30 h (H of 120-200 W m −2 ) and 11:00 h (LE of 230-480 W m −2 ), respectively.Both H and LE exhibited secondary peaks of 140 W m −2 and 245 W m −2 (ensemble averages), respectively, at 15:30 h.These midday troughs in ensemble average H and LE were attributed to the increasing energy advection of tidal waters (Fig. 7d) from an average of 5 W m −2 at 7:00 h to 160 W m −2 at 12:30 h.Later in the day, from 14:00 to 17:30 h, flood waters were a source of energy, with ∆H adv reaching a minimum of −125 W m −2 at 16:00 h.Discussion Paper | Discussion Paper | Discussion Paper | ) may not fully incorporate diurnal patterns in energy closure.For instance, during July to September 2004 and July and August 2005, average energy closure (Σ(R net − G)/Σ(H + LE), data not shown) was lowest (74 %) during Figures Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | −2 and −3 to 20 W m −2 , respectively.The storage terms were positively correlated with R net and, consequently, contributed to a reduction in available energy.Discussion Paper | Discussion Paper | Discussion Paper |

Fig. 1 .
Fig. 1.Landsat 7 thematic map false color composite (RGB bands 5,4,3) of southern Florida including the SRS6 study site and flux tower (site SRS6).Mangrove forests appear as bright green along the southwest coast and southern coast adjacent to the Florida Bay.

Fig. 2 .
Fig. 2.This conceptual diagram illustrates the key components of the daytime surface energy budget.(When considering the full diel cycles, the fluxes are bidirectional.)The H and LE represent the sensible and latent heat exchanges between the mangrove forest and the atmosphere.The G denotes the heat flow in or out of the soil, and S is the sum of heat and biochemical energy storage in biomass.The ∆H adv is the lateral energy transport to and from the adjacent river and is associated with tidal activity.
Figure 4. Half-hourly averages (solid lines) and ±1 s.d.(dashed lines) of net radiation (R net ; panel A), sensible (H; panel B) and latent (LE; panel C) heat fluxes, and soil heat flux (G; panel D) during July to September 2004 and July to August 2005.Flux data were partitioned into periods when the sediment was exposed (low tide) and when the surface was inundated (high tide).

Fig. 4 .
Fig. 4. Half-hourly averages (solid lines) and ±1 s.d.(dashed lines) of net radiation (R net ; A), sensible (H; B) and latent (LE; C) heat fluxes, and soil heat flux (G; D) during July to September 2004 and July to August 2005.Flux data were partitioned into periods when the sediment was exposed (low tide) and when the surface was inundated (high tide).

Fig. 5 .
Fig. 5. Water levels inundating the mangrove forest at three sites (Fig. 2) along a transect (A) and within the mouth of the tidal creek (B).Recharge at the mouth of the tidal creek (C) showing flow into the forest (recharge > 0) during flood tide and drainage (recharge < 0) into Shark River during ebb tides.