Positive Feedbacks in Seagrass Ecosystems: Implications for Success in Conservation and Restoration

Abstract Seagrasses are threatened by human activity in many locations around the world. Their decline is often characterized by sudden ecosystem collapse from a vegetated to a bare state. In the 1930s, such a dramatic event happened in the Dutch Wadden Sea. Before the shift, large seagrass beds (Zostera marina) were present in this area. After the construction of a large dam and an incidence of the “wasting disease” in the early 1930s, these meadows became virtually extinct and never recovered despite restoration attempts. We investigated whether this shift could be explained as a critical transition between alternative stable states, and whether the lack of recovery could be due to the high resilience of the new turbid state. We analyzed the depth distribution of the historical meadows, a long-term dataset of key factors determining turbidity and a minimal model based on these data. Results demonstrate that recovery was impossible because turbidity related to suspended sediment was too high, probably because turbidity was no longer reduced by seagrass itself. Model simulations on the positive feedback suggest indeed the robust occurrence of alternative stable states and a high resilience of the current turbid state. As positive feedbacks are common in seagrasses, our findings may explain both the worldwide observed collapses and the low success rate of restoration attempts of seagrass habitats. Therefore, appreciation of ecosystem resilience may be crucial in seagrass ecosystem management.     

Comparative Evidence that Salt Marshes and Mangroves May Protect Seagrass Meadows from Land-derived Nitrogen Loads

Seagrass meadows within estuaries are highly sensitive to increased supplies of nitrogen (N). The urbanization of coastal watersheds increases the delivery of N to estuaries, threatening seagrass habitats; both seagrass production per unit area and the area of seagrass meadows diminish as land-derived N loads increase. The damaging effects of land-derived N loads may be lessened where there are fringes of coastal wetlands interposed between land and seagrass meadows. Data compiled from the literature showed that production per unit area by seagrasses increased and losses of seagrass habitat were lower in estuaries with relatively larger areas of fringing wetlands. Denitrification and the burial of land-derived N within fringe wetlands may be sufficient to protect N-sensitive seagrass habitats from the detrimental effects of land-derived N. The protection furnished by fringing wetlands may be overwhelmed by increases in anthropogenic N loads in excess of 20–100 kg N ha⁻¹ y⁻¹. The relationships of land-derived N loadings, fringing coastal wetlands, and seagrass meadows demonstrate that different units of the landscape mosaic found in coastal zones do not exist as separate units, but instead are coupled and uncoupled by biogeochemical transformations and transport among environments. Received 12 December 2000; accepted 15 August 2001.     

Effects of herbivorous birds on intertidal seagrass beds in the northern Wadden Sea

During autumn migration (September to December), brent geese (Branta b. bernicla) and wigeon (Anas penelope) feed on the seagrass Zostera noltii in the nearshore, upper tidal zone leeward of the island of Sylt (eastern North Sea). To graze on leaves and shoots above the sediment and on rhizomes and roots below, these birds reworked the entire upper 1 cm layer of sediment eight times within this 3-month period. In addition, brent geese excavated pits 3–10 cm deep by trampling in order to feed on below-ground phytomass. About 12% of the seagrass beds became pitted to an average depth of 4.5 cm. Using net exclosures, it was estimated that birds removed 34 g dry weight m^–2 of above-ground and 28 g of below-ground phytomass. This corresponds to 45% of the phytomass in September. Of the overall loss of phytomass from September to December, 63% was caused by birds. Roughly half of the leaves fell off anyway until December and the other half were taken by the birds. Below the ground, phytomass remained almost constant where birds were excluded, while with birds phytomass of rhizomes and roots was halved. In spite of this strong effect, in the next vegetation period the blade density was lower at former exclosure sites compared to the ambient seagrass bed. The underlying process seems to be a self-inhibition of dense overwintering seagrass by mud accretion. Assuming our experimental results can be scaled up to the entire seagrass bed, we hypothesize that in the sheltered upper intertidal zone, seasonal erosion caused by herbivorous geese and ducks is necessary for the persistence of Z. noltii. Received: 7 January 1999 / Received in revised form: 23 August 1999 / Accepted: 25 August 1999     

Seagrass (Zostera spp.) as food for brent geese (Branta bernicla): an overview

Brent geese (called brant in North America) are among the smallest and the most marine of all goose species, and they have very long migration routes between high Arctic breeding grounds and temperate wintering grounds. Like all other geese, brent geese are almost entirely herbivorous. Because of these ecological characteristics they have a high food demand and are strongly dependent on stopover sites to ”refuel” during the migration period. Three subspecies of brent geese are distributed around the Holarctic, forming seven populations with distinct migration routes. Most or all of these populations make heavy use of Zostera spp. during migratory stopovers on spring and/or autumn migration. Examples of Zostera stopover areas being used by large numbers of brent geese for several weeks each year are Izembek Lagoon (Alaska), lagoons in Baja California, the German/Danish Wadden Sea, the Golfe du Morbihan (France), British estuaries, and the White Sea (Western Russian Arctic). Brent geese feed on Zostera wherever they can, but they can only reach the plants at low tide or in shallow water. Changes in Zostera abundance affect brent goose distribution, and the ”wasting disease” affecting Atlantic Zostera stocks during the 1930s was at least partly responsible for a steep decline in brent goose population sizes on both sides of the Atlantic. While Zostera is of outstanding importance as food for brent geese, the impact of the geese on Zostera stocks seems to be less important – at many sites, the geese consume only a small amount of the available Zostera, or, if they consume more, the seagrass can regenerate fully until the following season. Received: 6 December 1998 / Received in revised form: 6 August 1999 / Accepted: 9 August 1999     

Policy plans and management measures to restore eelgrass (Zostera marina L.) in the Dutch Wadden Sea

The Dutch Wadden Sea has been changed dramatically over the last centuries by human activities like land reclamation and different forms of fishery. This has, amongst other things, led to changes in the number of biological communities. One of the changes was the near extinction of eelgrass (Zostera marina L.) in the Dutch Wadden Sea. The deterioration of the area led to policy plans in the late 1980s that aimed at restoring the original natural communities of which the eelgrass community was one. This paper presents a restoration strategy which contains a selection procedure for suitable transplantation sites. The selection procedure is based on factors such as sediment composition, exposure time, current velocity and wave action. These were combined in a GIS-based map integrating these factors. One important action in the restoration process is to increase the number of freshwater discharge points to meet the requirements of the brackish water community in general and the growing conditions for eelgrass in particular. Received: 27 October 1999 / Received in revised form: 3 February 2000 / Accepted: 3 February 2000     

Habitat suitability of the Wadden Sea for restoration of Zostera marina beds

A conceptual model is proposed, describing potential Zostera marina habitats in the Wadden Sea, based on reported data from laboratory, mesocosm and field studies. Controlling factors in the model are dynamics, degree of desiccation, turbidity, nutrients and salinity. A distinction has been made between a higher and a lower zone of potential habitats, each suitable for different morphotypes of Z. marina. The model relates the decline of Z. marina in the Wadden Sea to increased sediment and water dynamics, turbidity, drainage of sediments (resulting in increased degree of desiccation) and total nutrient loads during the twentieth century. The upper and lower delineation of both the higher and the lower zone of potential Z. marina habitats appear to be determined by one or a combination of several of these factors. Environmental changes in one of these factors will therefore influence the borderlines of the zones. The lower zone of Z. marina will be mainly affected by increased turbidity, sediment dynamics, degree of desiccation during low tide and nutrient load. The higher zone will be affected by increases in water and sediment dynamics, desiccation rates and nutrient loads. Potential Z. marina habitats are located above approx. –0.80 m mean sea level (when turbidity remains at the same level as in the early 1990s) in sheltered, undisturbed locations, and preferably where some freshwater influence is present. At locations with a high, near-marine, salinity, the nutrient load has to be low to allow the growth of Z. marina. The sediment should retain enough water during low tide to keep the plants moist. Our results suggest that the return of Z. marina beds within a reasonable time-scale will require not only suitable habitat conditions, but also revegetation measures, as the changes in the environment resulting from the disappearance of Z. marina may impede its recovery, and the natural import of propagules will be unlikely. Furthermore, the lower zone of Z. marina may require a genotype that is no longer found in the Wadden Sea. Received: 26 April 1999 / Received in revised form: 15 October 1999 / Accepted: 16 October 1999     

The relative importance of food and shelter for seagrass-associated invertebrates: a latitudinal comparison of habitat choice by isopod grazers

The generality of mechanisms affecting habitat choice and grazing in seagrass meadows was evaluated in a latitudinal comparison of seagrass grazers from the temperate (60°N) Baltic Sea and the subtropical (30°N) Gulf of Mexico. Using similar habitat choice experiment set-ups in Finland and the USA, the role of food type, habitat complexity and predation hazard on habitat choice of the isopods Idotea baltica (Pallas) and Erichsonella attenuata Harger were tested. When shelter was provided by both living and artificial seagrass, epiphytic food resources on artificial vegetation were clearly preferred by both species, although Idotea was attracted to epiphyte-free seagrass when no alternative food was present. When choosing between food and shelter, both species preferred epiphytic food over shelter. However, under predation hazard of fish, Erichsonella clearly switched to the habitat offering shelter, while the presence of a predatory fish produced no preference for shelter by Idotea. Food type may be considered as an universal mechanism that partly determines the presence of grazers in seagrass habitats and is, in the absence of a predator, more important than shelter. Predation risk affected the behaviour of the grazers, but the response varied between species possibly due to varying importance of fish predation in the areas studied. Received: 16 November 1998 / Accepted: 13 February 1999     

The loss of seagrass in Cockburn Sound,Western Australia. II. Possible causes of seagrass decline

This paper examines possible reasons for the extensive loss of seagrass in Cockburn Sound following industrial development. Transplanted seedlings survived poorly in Cockburn Sound compared with an adjoining embayment. Altered temperature, salinity, sedimentation and water movement do not explain the death of seagrass over wide areas, and there is no evidence for a role of pathogens. Oil refinery effluent reduced seagrass growth in aquaria at concentrations similar to those at the point of discharge, but could not account for the widespread deterioration observed in the field. Severe grazing by sea urchins was observed on meadows already under stress and does not appear to be a primary cause of decline; caged, transplanted seedlings also deteriorated.Increased light attenuation by phytoplankton blooms may have affected the ddepth to which seagrasses could survive, but would have had little significant effect in shallow water; marked phytoplankton blooms were recorded only after extensive seagrass decline had taken place. Light reduction by enhanced growth of epiphytes and loose-lying blankets of filamentous algae in nutrient enriched waters is suggested as the most likely cause of decline. Heavy epiphyte fouling was consistently observed on seagrasses in deteriorating meadows, as well as on declining, transplanted seedlings, and is known to significantly impair photosynthesis in other systems. Extensive seagrass decline coincided with the discharge of effluents rich in plant nutrients.     

Was total primary production in the western Wadden Sea stimulated by nitrogen loading?

Borum and Sand-Jensen (1996) described empirical relationships between nitrogen (N) loadings from land and total (benthic + pelagic) primary production rates in shallow coastal marine waters. We applied these relationships to N loadings of the western Wadden Sea system, and compared the production estimates with actually observed primary production rates of autotrophic components (phytoplankton, microphytobenthos, macroalgae and seagrasses) for those years for which field data were available. During the 1980s and early 1990s, primary production values appear in good agreement with those derived from the empirical relationships. During the 1960s and early 1970s, however, these relationships substantially overestimated the total primary production in the western Wadden Sea. Based on ambient nutrient concentrations and the Redfield ratio, production in that period was considered not to be limited by N but by phosphorus (P) during most of the time. It is concluded that primary production is not invariably stimulated by N loading from land. If other factors (i.e. additional nutrient sources, N:P ratios, internal nutrient dynamics and co-limiting effects of nutrients and light) are not taken into account, management regulations that are targeted at diminishing the effects of eutrophication hold the risk of seriously under- or overestimating nutrient reductions that are thought necessary to achieve their goals. Received: 30 November 1998 / Received in revised form: 12 July 1999 / Accepted: 15 July 1999     

Trophic Transfers from Seagrass Meadows Subsidize Diverse Marine and Terrestrial Consumers

In many coastal locations, seagrass meadows are part of a greater seascape that includes both marine and terrestrial elements, each linked to the other via the foraging patterns of consumers (both predators and herbivores), and the passive drift of seagrass propagules, leaves, roots and rhizomes, and seagrass-associated macroalgal detritus. With seagrasses declining in many regions, the linkages between seagrass meadows and other habitats are being altered and diminished. Thus, it is timely to summarize what is known about the prevalence and magnitude of cross-habitat exchanges of seagrass-derived energy and materials, and to increase awareness of the importance of seagrasses to adjacent and even distant habitats. To do so we examined the literature on the extent and importance of exchanges of biomass between seagrass meadows and other habitats, both in the form of exported seagrass biomass as well as transfers of animal biomass via migration. Data were most abundant for Caribbean coral reefs and Australian beaches, and organisms for which there were quantitative estimates included Caribbean fishes and North American migratory waterfowl. Overall, data from the studies we reviewed clearly showed that seagrass ecosystems provide a large subsidy to both near and distant locations through the export of particulate organic matter and living plant and animal biomass. The consequences of continuing seagrass decline thus extend far beyond the areas where seagrasses grow.     

Rapid colonization of new habitats in the Wadden Sea by the ovoviviparousLittorina saxatilis (Olivi)

The intertidal periwinkleLittorina saxatilis completely lacks larval dispersal and adult vagility is low. Although this suggests a low dispersal rate,L. saxatilis is frequently found in recently established habitats “exotic” to the Wadden Sea. Populations occur on man-made structures like dikes, breakwater and groynes, some of which are not older than several years. Furthermore,L. saxatilis is found on marsh grassSpartina anglica, introduced to the Wadden Sea in the 1920s and 1930s, as well as on mats of green macroalgae, which have become an abundant feature on the tidal flats since the late 1970s. Seagrass beds are likely to be the original habitat ofL. saxatilis in the Wadden Sea. Since seagrass populations have dramatically declined over the last decades, colonization of new habitat types enabledL. saxatilis to maintain its Wadden Sea populations despite a changing environment. Colonizers can reach new habitats by means of passive transport, especially by rafting on macrophytes and by aerial dispersal attached to birds. In thew Wadden Sea, the ovoviviparously reproducingL. saxatilis has demonstrated its ability to successfully found new populations with only a few individuals. No reduction of genetic variablility (founder effect) was observed in recently established populations.     

Lebensraum Seegraswiese

Seagrass specialists in the Red Sea Seagrass meadows play important ecological and environmental roles. The high level of productivity, complex structure and rich diversity allows a lot of organisms to seek shelter, feed and use seagrass habitats as nursery ground. Several species show highly specialized adaptations to the seagrass environment. This article presents a selection of seagrass specialists in the Red Sea using different survival strategies like symbiosis, mimicry or camouflage.     

Varying foraging strategies of Labridae in seagrass habitats: Herbivory in temperate seagrass meadows?

The diets of five species of Labridae in south-western Australia were examined to determine whether: (1) grazing of seagrass and epiphytic algae is a prominent feature of the food web within the deeper seagrass meadows of this temperate region; (2) levels of grazing differ among different seagrass systems; and diets differ among these closely-related species. Fish were collected seasonally from three seagrass habitats mainly comprising either Posidonia sinuosa, Posidonia coriacea or Amphibolis griffithii between the summer of 1996/97 and spring of 1997. Consumption of considerable amounts of algae and seagrass by Odax acroptilus and seagrass by Haletta semifasciata indicates that macrophyte grazing by fish is a component of the trophic dynamics of south-western Australian seagrass meadows. O. acroptilus and H. semifasciata were both omnivorous, feeding on a range of epifauna, infauna and flora, whereas Siphonognathus radiatus, Neoodax balteatus and Notolabrus parilus were carnivorous, feeding predominantly on motile epifauna, such as molluscs and crustaceans. The level of macrophyte grazing is likely to be underestimated in temperate offshore meadows of P. sinuosa and A. griffithii where omnivorous labrids, monacanthids and terapontids are abundant. Stable isotope data for O. acroptilus from the study region suggest that animal prey is more important to tissue maintenance than macrophyte material. Macrophytes may be grazed to acquire attached animal prey or for fulfilling energy requirements. Based on the distribution of prey, it appears that species in A. griffithii meadows forage within and below the seagrass canopy, whilst species in P. sinuosa meadows are likely to forage towards the basal area of this seagrass.     

Seagrass recovery in the Northern Wadden Sea?

Aerial surveys on seagrass (Zostera spp.) indicate a three to fourfold increase in bed area from 1994 to 2006 with up to 100 km² or 11% of intertidal flats in the Northfrisian Wadden Sea (coastal eastern North Sea), observed at seasonal maximum in August when flying during low tide exposure 300 to 500 m above ground. When viewed from the air, difficulties in distinguishing between seagrass and green algae and a lack of contrast on dark-coloured mudflats are sources of error in areal estimates. Particularly the positioning of beds remote from shores was imprecise. However, the consistency in method over time gives confidence to the inferred positive trend which is opposite to the global pattern. Both, the spatial pattern and a recent decrease in storminess suggest that sediment stability is the key factor for seagrass dynamics in this tidal area. On exposed sand flats, high sediment mobility may be limiting and along the sheltered mainland shore land claim activities with high accretion rates may cause a scarcity of seagrass. The potential area of seagrass beds may be twice as large as the realized maximum in 2006 but eventually the rising sea level will reverse the observed seagrass expansion.     

Solar radiation and tidal exposure as environmental drivers of Enhalus acoroides dominated seagrass meadows

There is strong evidence of a global long-term decline in seagrass meadows that is widely attributed to anthropogenic activity. Yet in many regions, attributing these changes to actual activities is difficult, as there exists limited understanding of the natural processes that can influence these valuable ecosystem service providers. Being able to separate natural from anthropogenic causes of seagrass change is important for developing strategies that effectively mitigate and manage anthropogenic impacts on seagrass, and promote coastal ecosystems resilient to future environmental change. The present study investigated the influence of environmental and climate related factors on seagrass biomass in a large ≈250 ha meadow in tropical north east Australia. Annual monitoring of the intertidal Enhalus acoroides (L.f.) Royle seagrass meadow over eleven years revealed a declining trend in above-ground biomass (54% significant overall reduction from 2000 to 2010). Partial Least Squares Regression found this reduction to be significantly and negatively correlated with tidal exposure, and significantly and negatively correlated with the amount of solar radiation. This study documents how natural long-term tidal variability can influence long-term seagrass dynamics. Exposure to desiccation, high UV, and daytime temperature regimes are discussed as the likely mechanisms for the action of these factors in causing this decline. The results emphasise the importance of understanding and assessing natural environmentally-driven change when interpreting the results of seagrass monitoring programs.     

Predicting the cumulative effect of multiple disturbances on seagrass connectivity

The rate of exchange, or connectivity, among populations effects their ability to recover after disturbance events. However, there is limited information on the extent to which populations are connected or how multiple disturbances affect connectivity, especially in coastal and marine ecosystems. We used network analysis and the outputs of a biophysical model to measure potential functional connectivity and predict the impact of multiple disturbances on seagrasses in the central Great Barrier Reef World Heritage Area (GBRWHA), Australia. The seagrass networks were densely connected, indicating that seagrasses are resilient to the random loss of meadows. Our analysis identified discrete meadows that are important sources of seagrass propagules and that serve as stepping stones connecting various different parts of the network. Several of these meadows were close to urban areas or ports and likely to be at risk from coastal development. Deep water meadows were highly connected to coastal meadows and may function as a refuge, but only for non‐foundation species. We evaluated changes to the structure and functioning of the seagrass networks when one or more discrete meadows were removed due to multiple disturbance events. The scale of disturbance required to disconnect the seagrass networks into two or more components was on average >245 km, about half the length of the metapopulation. The densely connected seagrass meadows of the central GBRWHA are not limited by the supply of propagules; therefore, management should focus on improving environmental conditions that support natural seagrass recruitment and recovery processes. Our study provides a new framework for assessing the impact of global change on the connectivity and persistence of coastal and marine ecosystems. Without this knowledge, management actions, including coastal restoration, may prove unnecessary and be unsuccessful.     

Tidal impact on planktonic primary and bacterial production in the German Wadden Sea

 Tidal variation of biological parameters was studied at three anchor stations in selected inlet channels of the northern German Wadden Sea in May and July 1994. Concentrations of bacteria, chlorophyll a and suspended matter as well as primary and bacterial production were assessed over a period of 25 h in the surface and in the bottom water. Diurnal variation in primary production was found both under in situ light conditions and under constant illumination. Tidal turbulence caused the introduction of detritus, bacteria and pigments from the sediment into the water column. The impact of sediment resuspension was most evident in the bottom water, leading to tidally oscillating bacterial production rates which were high during high stream velocity and low during the slack times. Estimations of the areal daily phytoplankton production and corresponding bacterial carbon demands were unbalanced. Primary production accounted for only 25–45% of the total bacterial carbon requirement. This discrepancy is due to the shallow euphotic depth in the Wadden Sea, allowing net primary production only in the upper 2–3 m of the water column, while the relatively high levels of bacterial activity do not show a vertical decline. Assuming that the specific biological activities in the water columns over the tidal flats are similar to those found in the inlet channels, it was found that production processes dominate in shallow areas whereas decomposition processes dominate in the deep channels. Moreover, the predominance of heterotrophic processes in the inlet channels means that additional organic carbon sources must contribute to the heterotrophic metabolism in the deep parts of the Wadden Sea, and that the horizontal flux of material is important in this turbid mesotidal ecosystem. Received: 18 April 1998 / Accepted: 12 November 1998     

Distribution patterns of bacterioplankton and chlorophyll-a in the German Wadden Sea

 In a first synoptic evaluation, the temporal and spatial distribution of bacterioplankton and chlorophyll-a were determined in the German Wadden Sea. Three surveys were undertaken in winter, spring, and summer of 1994 using up to eight ships simultaneously between the river Ems and Sylt island. Despite intensive hydrodynamic mixing of the Wadden Sea water, spatial gradients were obvious. The abundance of bacterioplankton ranged from 0.4 to 26×10⁵ ml^–1 and chlorophyll-a varied between <0.1 and 79 μg l^–1. In winter, relatively homogeneous distribution patterns of both parameters with small gradients were found. Highest chlorophyll-a values connected with a highly patchy structure were observed in spring, while in summer both total chlorophyll-a values and the complexity of the distribution pattern had decreased. In contrast, bacterial numbers increased steadily from January to July with the highest bacterial densities and greatest patchiness observed in summer. Moreover, in some regions of the Wadden Sea, a trophic succession of algae as carbon producers and bacteria as consumers was evident. Correlation analysis verified the relationship between bacteria and chlorophyll a, indicating bottom-up control of bacterial abundance in the northern part of the German Wadden Sea. Since the observed regression slope is remarkably low (0.12–0.46) compared to literature values (0.5–0.8), we suggest that the link between phytoplankton and bacteria found here is a special characteristic of the Wadden Sea as a transition zone between the coastal region and the outer North Sea. Received: 26 May 1998 / Accepted:12 November 1998     

Mercury pollution in the Ems estuary

From approximately 1960 to 1975 the Ems estuary received several tons of mercury per year from a chlor-alkali plant, a pesticide factory and some minor sources. The discharge has been reduced drastically from 1976 onwards. In 1975 and 1976 measurements were made on the distribution of mercury in the sediment. The horizontal distribution revealed a strong local enrichment of the sediment near the point of discharge. The vertical distribution was found to be in accordance with the local deposition rates. In the water phase no significant change in mercury content from 1975 to 1978/79 could be demonstrated. In 1978/79 a difference between Ems estuary and Dutch Wadden Sea was not significant. In 1978 mercury contents of eelpoutZoarces viviparus in the Ems estuary were about twice as high as in the Wadden Sea. In the Ems estuary a decrease of these contents was found between 1974/75 and 1978. A similar decline in the Wadden Sea may be related to a decreased mercury discharge by the River Rhine.     

Effects of heavy rainfall on Thalassia testudinum beds

In December 1999 heavy continuous rains that lasted one week affected the Venezuelan coastline. At Morrocoy National Park, a large marine reserve, rainfall values surpassed previous 32-year records and led to a decrease of salinity to 3 psu, which lasted for over a month at some locations. This study examined effects of these changes on the shallow-water meadows of the seagrass Thalassia testudinum Banks ex Köning (1805), by comparing their structure before and after this disturbance at four selected sites. The rain acted as a pulse-type disturbance, altering the physicochemical features at all sites, which soon returned to the previously prevailing conditions. However, T. testudinum beds showed a sudden stress reaction followed by slow recovery. The disturbance prompted an increase in the amount of dead tissue and defoliation. Later a sustained increase of leaf biomass, productivity and reproductive shoots was observed, neither ever noticed before in the Park. The seagrass meadows in Morrocoy showed signs of stress even one year after the impact, suggesting that the 1999 disturbance deeply affected the characteristics of these systems within the Park.