Shifts in the relative abundance of ammonia-oxidizing bacteria and archaea across physicochemical gradients in a subterranean estuary

Submarine groundwater discharge to coastal waters can be a significant source of both contaminants and biologically limiting nutrients. Nitrogen cycling across steep gradients in salinity, oxygen and dissolved inorganic nitrogen in sandy 'subterranean estuaries' controls both the amount and form of nitrogen discharged to the coastal ocean. We determined the effect of these gradients on betaproteobacterial ammonia-oxidizing bacteria (β-AOB) and ammonia-oxidizing archaea (AOA) in a subterranean estuary using the functional gene encoding ammonia monooxygenase subunit A ( amoA ). The abundance of β-AOB was dramatically lower in the freshwater stations compared with saline stations, while AOA abundance remained nearly constant across the study site. This differing response to salinity altered the ratio of β-AOB to AOA such that bacterial amoA was 30 times more abundant than crenarchaeal amoA at the oxic marine station, but nearly 10 times less abundant at the low-oxygen fresh and brackish stations. As the location of the brackish mixing zone within the aquifer shifted from landward in winter to oceanward in summer, the location of the transition from a β-AOB-dominated to an AOA-dominated community also shifted, demonstrating the intimate link between microbial communities and coastal hydrology. Analysis of ammonia-oxidizing enrichment cultures at a range of salinities revealed that AOA persisted solely in the freshwater enrichments where they actively express amoA . Diversity (as measured by total richness) of crenarchaeal amoA was high at all stations and time points, in sharp contrast to betaproteobacterial amoA for which only two sequence types were found. These results offer new insights into the ecology of AOA and β-AOB by elucidating conditions that may favour the numerical dominance of β-AOB over AOA in coastal sediments.     

Changes in community structure of active protistan assemblages from the lower Pearl River to coastal Waters of the South China Sea

Protists make up an important component of aquatic ecosystems, playing crucial roles in biogeochemical processes on local and global scales. To reveal the changes of diversity and community structure of protists along the salinity gradients, community compositions of active protistan assemblages were characterized along a transect from the lower Pearl River estuary to the open waters of the South China Sea (SCS), using high-throughput sequencing of the hyper-variable V9 regions of 18S rRNA. This study showed that the alpha diversity of protists, both in the freshwater and in the coastal SCS stations was higher than that in the estuary. The protist community structure also changed along the salinity gradient. The relative sequence abundance of Stramenopiles was highest at stations with lower salinity and decreased with the increasing of salinity. By contrast, the contributions of Alveolata, Hacrobia and Rhizaria to the protistan communities generally increased with the increasing of salinity. The composition of the active protistan community was strongly correlated with salinity, indicating that salinity was the dominant factor among measured environmental parameters affecting protistan community composition and structure.     

Shift of Bacterial Community Structures in Sediments From the Changjiang (Yangtze River) Estuary to the East China Sea Linked to Environmental Gradients

Abstract

The Changjiang estuary and its adjacent East China Sea (ECS) have been considered as one of the most dynamic areas significantly contributing to elemental exchanges globally. The purpose of this study was to understand the alteration of microbial consortia at the interface of riverine and coastal environments in relation to environmental variations as well as their roles in biogeochemical cycling at this dynamic region. We sampled surface sediment samples at 4 stations from the estuary to coastal regions of the ECS. Along with collections of physicochemical parameters, we sequenced bacterial 16S rRNA genes of clones from each sample. Results showed a distinct transition of bacterial community from typical freshwater sediment phyla (e.g., Betaproteobacteria and Firmicutes) to those commonly inhabited in saline environments (e.g., Deltaproteobacteria and Gammaproteobacteria). The bacterial group at the transition zone characterized by high accumulation of organic matters and intense mixing of riverine and coastal waters was most diverse. Bacterial community structures at two ECS stations showed a similar pattern but contained different dominant taxa, shifting from Deltaproteobacteria-affiliated sulfate-reducing bacteria at the station closer to the shore to Gammaproteobacteria-affiliated nitrate-reducing bacteria further offshore. It suggested that the sedimentary bacterial community structure was related to salinity, sediment type, and substrate availability and composition.     

Fish species richness decreases with salinity in tropical coastal lagoons

Aim To analyse the relationship between fish species richness and salinity, and to provide a simple linear model for fish diversity trends across salinity gradients in a tropical coastal lagoon that can be compared with other similar ecosystems and other communities. To reinforce our conclusions, the salinity–fish richness relationship was investigated at different spatial scales (sampling station, set of stations and whole lagoon) and for two different periods, separated by 18 years. Location The Terminos coastal lagoon, a shallow tropical lagoon (mean maximum depths ranging between 3.5 and 4.5 m), is located in the southern Gulf of Mexico (18.5–18.8° N, 91.3–91.9° W). The lagoon is 70 km long and 30 km wide, with a surface area of 1700 km². Methods Fish sampling, individual identification to the species level, and environmental variable measurements were carried out monthly at 17 sampling points. Multiple regression analysis with a backward selection procedure was used to relate fish species richness to environmental variables. Other statistical techniques, including cluster analysis and ancova , were applied to experimental data surveys. Results Among the different environmental variables, salinity was significantly and consistently related to fish species richness, whatever the period and the scale of observation. We found mainly significant negative correlations (P < 0.05) between fish species richness and salinity when sampling stations were analysed individually, and particularly for the river runoff zones with high variation in salinity throughout the year. For the entire lagoon, robust negative linear models were observed when fish species richness was organized into salinity ranges, with salinity explaining c. 8% of the variation in mean fish species richness (in a multiple regression analysis; 63–93% when considered in isolation). Main conclusions In the Terminos lagoon the relationship between fish species richness and salinity is mainly negative on any spatial scale. This result may be due partially to the penetration of freshwater fishes into estuarine areas following freshwater discharges, and partially to the dominance of estuarine taxa more able to tolerate low than high salinity values. Finally, we suggest that the ‘realized’ ecotone, where species from different origins really mix, is situated between 5 and 10‰, corresponding to the highest fish richness.     

The benthic macrofauna along the estuarine gradient of the Schelde estuary

The intertidal benthic macrofauna of the Schelde estuary (The Netherlands and Belgium) was sampled in late autumn of 1990 at 50 stations along the whole salinity gradient (between Vlissingen and Dendermonde), including the freshwater tidal part. All stations were situated in sheltered areas with a relatively muddy sediment. Species richness, diversity and total biomass of the benthic macrofauna decreased along the salinity gradient from Vlissingen to Dendermonde, while total density showed no clear trend. Especially the oligohaline and freshwater tidal part of the Schelde estuary was characterized by a very impoverished benthic community, composed only of Oligochaeta. No other species (freshwater, marine or brackish) was observed in this part of the estuary. The marine part had a more diverse macrozoobenthos structure than that of the brackish part. Species found only in the marine zone areCerastoderma edule, Tharyx marioni, Eteone longa, Nephtys hombergii andCapitella capitata. In the brackish part of the estuary,Corophium volutator was a typical, dominant species. However, a lot of the dominant species were common in both the marine and brackish part of the Schelde estuary (e.g. Heteromastus filiformis, Pygospio elegans, Nereis diversicolor, Macoma balthica). The observed gradient in species composition and dominance is compared with some other European estuaries. The marine and brackish part of the Schelde estuary is quite similar to other european estuaries. The freshwater tidal part, however, was more impoverished.     

Influence of salinity on prevalence of the parasite Loxothylacus panopaei in the xanthid Panopeus obesus in SW Florida

This study was conducted to examine the potential influence of salinity, a proxy for freshwater inflow, on the prevalence of the castrator parasite Loxothylacus panopaei on saltmarsh mud crabs Panopeus obesus on SW Florida oyster reefs. Spatial and seasonal patterns of the presence of potential host crabs and the prevalence of the parasite were assessed in the Caloosahatchee, Estero, and Faka Union estuaries. Lift nets (1 m2) containing 5 1 of oyster clusters were deployed on intertidal reefs at 3 sites along the salinity gradient of each estuary. Nets were deployed during 3 seasonally dry and 3 seasonally wet months for a period of 30 d. P. obesus densities tended to increase downstream in higher salinity waters, with crabs being absent from the upper station in the Caloosahatchee during both seasons and absent from the upper station of the Faka Union during wet months. Parasite prevalence was reduced upstream in each estuary during wet months compared to dry months, and for those estuaries that experienced higher relative levels of freshwater inflow. Furthermore, parasite prevalence was positively correlated with the mean salinity of capture of host crabs. Based on the distribution of P. obesus and the above patterns related to salinity, it appears that freshwater inflow and seasonal rains might regulate the prevalence of this parasite in SW Florida by creating spatiotemporal, low salinity refuges for its host.     

Comparative study of the hyperbenthos of three European estuaries

The hyperbenthic fauna of the subtidal channels of the Eems (N. Netherlands), Westerschelde (S.W. Netherlands), and Gironde (S.W. France) estuaries was sampled within a 15-day period in summer 1991. In each estuary, quantitative samples were taken at regularly spaced stations covering the entire salinity gradient from marine conditions at the mouth to nearly freshwater conditions upstream. The diversity of the samples and the distribution of the species along the main estuarine gradients were assessed. Hyperbenthic communities were identified using different multivariate statistical techniques. The species composition and the density and biomass of the dominant species of each community were compared among communities.     

Biological and chemical responses in a temporarily open/closed estuary to variable freshwater inputs

In coastal lagoons with occasional connection to oceans, variations in physicochemical conditions and biological responses can be pronounced. To examine the influence of variable rainfall and tidal flushing, we measured, over a 4-year period, salinity, temperature and dissolved oxygen, and fish abundances, in Devereux Slough, a coastal lagoon occasionally connected to the Pacific Ocean along the California coast. We test the hypotheses that salinity is the primary influence on fish composition, and that fish density is affected by freshwater discharge and by berm breaches. During our sampled years, annual rainfall varied from 188 to 971 mm, and the sand berm separating the Slough from the ocean breached in each year except 2007, a drought period. Average yearly salinity ranged from 7.7 to 37.1 ppt. Hypoxic conditions in the near-bottom water were common each year. The best predictor of the fish composition was salinity, and an indirect correlation with fresh water discharge was responsible for much of the temporal variation in the fish assemblage. The interaction between salinity, state of the estuary mouth (open vs. closed), and precipitation significantly predicted densities of Fundulus parvipinnis (Girard 1984).     

广东沿岸海域鱼类群落排序

根据广东沿岸海域春秋两季底拖网鱼类采样数据,运用多维尺度转换分别对两季的鱼类样品进行排序。排序揭示出的鱼类群落格局及其季度差异与环境变异性密切相关。同处混合水区域的站位鱼类组成较为相似;分布在珠江冲淡水和外海高盐水区域的站位,鱼类组成则与多数沿岸站位有明显差异。春季沿岸海域鱼类组成有一东北－西南向的变化趋势,这一群落格局是由于该海域东北部受低温东海沿岸流影响所致;秋季珠江河口区受冲淡水的影响,而调     

Palaeolimnological evidence for the independent evolution of neighbouring terminal lakes,the Murray Darling Basin,Australia

Phytoplankton composition and production are highly unpredictable within an estuary, due to the high variability of forcing factors, such as freshwater flow, salinity, nutrients and light. The Guadiana estuary has shown sharp inter-annual differences in freshwater flow, related to variable precipitation, which is expected to affect nutrient loadings, light availability and phytoplankton succession. Water retention due to dam construction will further enhance changes in river flow and ecosystem dynamics. The main goal of the present study was to describe and relate phytoplankton succession and environmental conditions, namely nutrients and light, in the Guadiana upper estuary (south-western Iberian Peninsula), a dam regulated temperate estuary. From March 2004 to October 2005, water samples were collected in three stations along a longitudinal transect covering the upper estuary. Several water variables were determined and phytoplankton composition was studied through inverted and epifluorescence microscopy. A typical freshwater phytoplankton succession was observed, from a diatom spring bloom to cyanobacteria dominance in the summer, and a second diatom bloom in the autumn. Neither nutrients nor light availability seemed to be related to the observed succession, especially the seasonal variation of diatom abundance. During summer, nutrient concentrations (especially Si) were high and non-limiting, whilst light was available in the mixing layer. However, diatoms were present in low numbers. Grazing pressure was probably responsible for the regulation of diatom seasonal succession in the Guadiana upper estuary, which should be addressed in future studies. Handling editor: K. Martens     

Comparative analysis of reproductive traits in black-chinned tilapia females from various coastal marine, estuarine and freshwater ecosystems

The black-chinned tilapia Sarotherodon melanotheron is a marine teleost characterised by an extreme euryhalinity. However, beyond a certain threshold at very high salinity, the species exhibits impaired growth and precocious reproduction. In this study, the relationships between reproductive parameters, environmental salinity and condition factor were investigated in wild populations of this species that were sampled in two consecutive years (2003 and 2004) from three locations in Senegal with different salinities: Guiers lake (freshwater, 0 psu), Hann bay (seawater, 37 psu) and Saloum estuary (hypersaline water, 66-127 psu). The highest absolute fecundity and spawning weight were recorded in seawater by comparison to either freshwater or hypersaline water whereas the poorest condition factors were observed in the most saline sampling site. These results reflect higher resource allocation to the reproduction due to the lowest costs of adaptation to salinity in seawater (the natural environment of this species) rather than differences in food resources at sites and/or efficiency at foraging and prey availability. Fecundities, oocyte size as well as spawning weight were consistent from year to year. However, the relative fecundity in the Saloum estuary varied significantly between the dry and rainy raisons with higher values in the wet season, which seems to reflect seasonal variations in environmental salinity. Such a reproductive tactic of producing large amounts of eggs in the rainy season when the salinity in the estuary was lower, would give the fry a better chance at survival and therefore assures a high larval recruitment. An inverse correlation was found between relative fecundity and oocyte size at the two extreme salinity locations, indicating that S. melanotheron has different reproductive strategies in these ecosystems. The adaptive significance of these two reproductive modes is discussed in regard to the heavy osmotic constraint imposed by extreme salinities and high inter-specific competition.     

Estuarine fish communities respond to climate variability over both river and ocean basins

Estuaries are dynamic environments at the land–sea interface that are strongly affected by interannual climate variability. Ocean–atmosphere processes propagate into estuaries from the sea, and atmospheric processes over land propagate into estuaries from watersheds. We examined the effects of these two separate climate‐driven processes on pelagic and demersal fish community structure along the salinity gradient in the San Francisco Estuary, California, USA. A 33‐year data set (1980–2012) on pelagic and demersal fishes spanning the freshwater to marine regions of the estuary suggested the existence of five estuarine salinity fish guilds: limnetic (salinity = 0–1), oligohaline (salinity = 1–12), mesohaline (salinity = 6–19), polyhaline (salinity = 19–28), and euhaline (salinity = 29–32). Climatic effects propagating from the adjacent Pacific Ocean, indexed by the North Pacific Gyre Oscillation (NPGO), affected demersal and pelagic fish community structure in the euhaline and polyhaline guilds. Climatic effects propagating over land, indexed as freshwater outflow from the watershed (OUT), affected demersal and pelagic fish community structure in the oligohaline, mesohaline, polyhaline, and euhaline guilds. The effects of OUT propagated further down the estuary salinity gradient than the effects of NPGO that propagated up the estuary salinity gradient, exemplifying the role of variable freshwater outflow as an important driver of biotic communities in river‐dominated estuaries. These results illustrate how unique sources of climate variability interact to drive biotic communities and, therefore, that climate change is likely to be an important driver in shaping the future trajectory of biotic communities in estuaries and other transitional habitats.     

福建敖江口表层沉积硅藻空间分布特征

为探讨福建敖江口表层沉积硅藻空间分布特征,2019年7月对敖江口进行表层沉积硅藻的采样调查,并研究了硅藻与环境因子的关系。结果表明,从13个站点共检出硅藻114种,隶属于39属。硅藻丰度具有从河口向外海先减少后增加的变化特征。聚类分析表明,主要硅藻属种可划分为淡水种组合带和半咸水-咸水种组合带。典型对应分析（CCA）表明,表层海水温度和盐度是影响硅藻分布的主要环境变量。河口区盐度相对较低,主要分布淡水种双面曲壳藻、优美曲壳藻和颗粒沟链藻;外海区北部盐度相对较高,主要分布咸水种流水双菱藻;外海区南部盐度相对较低,主要分布淡水种优美曲壳藻和颗粒沟链藻;滩涂的沉积物较粗,主要分布优美曲壳藻。此外,河口区和外海区南部可能存在一定的水体污染。     

Effects of temperature on growth of Vallisneria americana in a sub-tropical estuarine environment

The submersed aquatic vegetation (SAV) species Vallisneria americana Michx. (tape grass) is a valuable resource in the Caloosahatchee estuary and in many other aquatic systems. Given the variable nature of freshwater inflows and environmental conditions in the Caloosahatchee, it is necessary to understand how tape grass will respond to high and low salinity conditions at different light and temperature levels. Specifically, quantitative information is needed as input to modeling tools that can be applied to predict growth and survival of tape grass under a range of environmental conditions present in the estuary. We determined growth rates for small and medium sized tape grass plants obtained from the Caloosahatchee estuary, southwest coastal Florida, USA in freshwater (0.5 psu) under high (331 μE m^?2 s^?1) and low light (42 μE m^?2 s^?1) and at 10 psu under high light conditions. We ran six treatments at five temperatures spanning 13–32 °C for 8–9 weeks. The optimum temperature for growth was roughly 28 °C, with a minimum threshold temperature of 13 °C and a maximum threshold temperature of 38 °C. Plants grew fastest in freshwater, at high light and temperatures greater than 20 °C. The slowest growth rates were observed at 13 °C regardless of salinity, light or plant size. Our results suggest that tape grass growth is strongly influenced by water temperature and that additional stressors such as low light and elevated salinity can reduce the range of temperature tolerance, especially at colder water temperatures.     

Fish community response to increased river flow in the Kariega Estuary,a freshwater-deprived,permanently open southern African system

The littoral and demersal ichthyofaunal community structure in the freshwater-deprived, permanently open Kariega Estuary was investigated following heavy rain in November 2006 and was compared to low-flow condition data from 1991 and 1996. All surveys took place during the spring months and allowed for a comparison of a wet and a dry spring period. The 2006 freshwater pulse generated a strong horizontal salinity gradient within the estuary. In the absence of freshwater inflow, the ichthyofaunal community in the littoral zone was numerically dominated by estuarine resident species, whilst after the freshwater pulse an increased contribution of marine migrant species was observed. Within the demersal zone, marine straggler species dominated during the dry spring period and estuarine residents during the wet spring period. Numerical analyses of the littoral and demersal fish assemblages indicated the presence of three distinct groupings — corresponding to the upper and middle reaches during separate wet and dry periods, and a community associated with the lower reaches of the estuary. It is suggested that the shift in community structure between the dry and wet spring periods could be related to altered physico-chemical and trophic conditions within the estuary, as well as the increased presence of freshwater and estuarine olfactory cues within the coastal zone, which would have resulted in the recruitment of 0+ estuary-associated marine species into the Kariega system.     

Associations of testate rhizopods (Protozoa) in the plankton of a Malaysian estuary and two nearby ponds

Plankton samples were collected from the Chukai-Kemaman estuary in Malaysia in order to determine the distribution of testate rhizopods in relation to salinity. Two nearby freshwater ponds were sampled for comparison.
In the ponds, 35 species of testate rhizopods were found, 13 of which were not found in the estuary. From the estuary 53 species were found, of which 31 were not found in the ponds. Some species appeared to have been lifted into the plankton by the rising tide. At a generic level, the Arcella species were very similar in both ponds and estuary (Sorensen Index 80), the Difflugia species were moderately similar (Sorensen Index 47), while Nebela and Quadrullela were present in the estuarine samples, but absent from the pond samples.
The salinity gradient ranged from sea water down to a conductivity of 27 μS. All the estuarine stations were tidal. The first freshwater testate rhizopods were found in a region where the conductivity was between 3000 and 4000 μS at high tide. Where the conductivity was below 1000 μS at high tide the number of species rapidly increased, and reached a maximum of 25 in the samples from the lowest conductivities. The flowering tree, Hibiscus tiliaceus , appears to be an indicator of the region where the first freshwater testate rhizopods might be encountered upstream from the sea.     

Spatio-temporal distribution of early life stages of the European anchovy Engraulis encrasicolus L. within a European temperate estuary with regulated freshwater inflow: effects of environmental variables

The spatio-temporal distribution of the anchovy Engraulis encrasicolus in its early life stages was related to environmental conditions within the Guadalquivir River estuary (south-west, Spain) by monthly field surveys during nine periods of recruitment (May 1997 to December 2005). Anchovy post-larvae showed a consistent seasonal pattern of abundance throughout the study period: each year, a high anchovy recruitment period (HARP) occurred from late May to November, with a main peak in July, coinciding with the period when environmental conditions were more stable. Results of stepwise multiple regression analysis indicates that density of its main prey, Mesopodopsis slabberi, explained 45% of total anchovy density variance. Furthermore, after removing the effect of this variable, interannual differences in the anchovy estuarine recruitment were not significant. Clear spatial and tidal trends were also observed for both prey and predator: at each sampling date, density decreased from the outer to inner estuary; at each sampling site, density was higher during ebbs than during floods. Field distributions related to environmental gradients during HARP indicated that the populations of E. encrasicolus and M. slabberi seemed to hold a steady position at a point on the salinity gradient by longitudinal displacement within the estuary. Since freshwater management actions affect the longitudinal position of the salinity gradient as well as the input of nutrients to the estuary and adjacent coastal areas, it is hypothesized that this factor may also be relevant to anchovy recruitment.     

Trophic structure of macrobenthos in the Tagus estuary and adjacent coastal shelf

The trophic structure of benthic communities in the Tagus estuary and adjacent coastal shelf was characterized according to a functional guild approach, based on sampling surveys conducted between 1987 and 2000. Macrobenthic organisms were assigned to seven distinct trophic groups (herbivorous, filter feeders, surface deposit feeders, subsurface deposit feeders, carnivores, filter feeders/detritivores, carnivores/detritivores) and the dominance of these groups was related to environmental variables using multivariate ordination techniques. Surface-deposit feeders were numerically dominant in the Tagus estuary, making up 52% of the benthic communities, while in the adjacent coastal shelf the assemblage was dominated by both surface-deposit feeders and filter feeders (37% and 33%, respectively). When biomass was considered, filter feeders and filter feeders/detritivores were the dominant groups in the estuary, while for the adjacent coastal shelf filter feeders represented 83% of the total biomass. Salinity, depth and sediment composition were the main factors structuring spatial distribution. Surface-deposit feeders were the most abundant macrobenthos of the upper estuary. Surface deposit feeders also dominated the middle and the lower estuary but the proportion of filter feeders as well as other trophic groups increased with salinity. Generally, a more even distribution of trophic structure was found at stations with high salinity. In the adjacent coastal shelf, the trophic diversity decreased with depth. The trophic structure revealed that filter feeders dominated in abundance and biomass in shallow sandy sediments (<25 m), while in deeper sandy mud and muddy habitats (>50 m to 260 m), deposit feeders and carnivores were the most important groups in abundance and biomass, respectively.     

我国东南沿海亚历山大藻休眠孢囊的分布和萌发研究

对4个海域的塔玛亚历山大藻(Alerandrium tamarense)和链状亚历山大藻(A．catenella)休眠孢囊的分布及萌发进行了研究．结果表明,厦门港仅在X1和X2站位有分布,且密度很小(0．4个·g-1);广西只在G2站位有发现,密度较少(2．5个·g-1泥样)．闽江口有3个站位有分布,M4站位的4～6cm层密度最大,达到6个·g-1泥样;长江口的孢囊分布广、密度大,DG-26站位的8～10cm层孢囊密度达到了23．2个·g-1泥样．孢囊的分布与沉积物底质类型、沉积速率、海流都有一定的关系．光照对孢囊萌发没有影响,温度升高导致萌发率和存活率均增大,而萌发时间缩短;在低氧条件下(0．01mgO2L-1),孢囊萌发率为0．亚历山大藻孢囊在合适的环境条件下终年都会萌发     

Changes in rocky reef fish assemblages throughout an estuary with a restricted inlet

Rocky reef habitat is common in many estuaries, yet its role as a habitat for fishes is poorly understood. There is also limited understanding of how access of coastal species into estuaries and habitat quality can affect the distribution of rocky reef fishes within estuaries. This study used baited remote underwater video stations to determine spatial patterns in fish assemblages associated with rocky reef habitat throughout a barrier estuary with a permanently open but restricted inlet. Estuarine rocky reefs provided habitat for a diverse assemblage of fishes, many of which were large juveniles and subadults. In the absence of a pronounced salinity or temperature gradient, a clear transition in fish assemblages occurred from coastal waters, through the inlet channel, to the central estuary, and into the inner estuary. The inlet channel, notably its narrowness and length, limits tidal input into this estuary, which acts as a significant impediment to the dispersal of many coastal fishes, and insufficient habitat excludes many coastal rocky reef species from the inner estuary. This study highlights the need to recognise estuarine rocky reefs as providing habitat for diverse fish assemblages and the role inlets play in restricting access of coastal species.