International Estuaries “Different Places but the Same Theme”

Overview Estuary function is the same world-wide Outside of estuaries in the United States, international estuaries are just as diverse We will focus on an estuary in each of the major continents (an example and some key factors) These factors will include: geology, physical characteristics and unique biological interactions

An Estuary Down Under - Swan River Key Characteristics: Is considered a tide-dominated estuary with tidal ranges up to 4 meters There has been a decrease in freshwater flow into the main opening of the estuary It is divided into the upper, middle and lower estuarine areas (Neira et al. 1992)

Swan River There are significant seasonal effects on this estuary in terms of salinity The lower part of the estuary can range in salinity from 35 PPT to 5 PPT (depending on the weather episode - drought vs. monsoonal patterns) Over 80% of the larval species spawn in marine waters

Swan River The hydrology changed back in the early 1900s when it was dredged closer to the mouth of the estuary, thus allowing a greater push of salt water up river Hamilton et al. 2001

Swan River As a result of the infiltration of Indian Ocean water into Swan River, there is a salt wedge that forms (but it is not well mixed) It was classified as meso/ eutrophic back in the 1990’s Development pressure and urban sprawl are contributing factors to the changes (in Hamilton et al. 2001)

Swan River Changes in the salt wedge vary greatly each season... The dry summer months allow for intrusion of the high salinity water to 50 km The wet months (winter)push less-salty water toward the mouth of the river with a salt wedge influence between 5 and 20 km A “typical tidal influence would be 2 – 3 km”

The increase in salinity… Swan River study taken at the barge site (Hamilton et al. 2001).

What does this mean? There are changes in the hydrology of Swan River These changes produce a salt-wedge with a bottom layer that is lower in dissolved oxygen Also, the increase in salt water upstream, seasonally, impacts the phytoplankton communities (shifts in primary productivity levels) A better look at the Swan River

A European Estuary – Venice, Italy Lazzari et al. 2004

Venice – a series of canals Image NASA.gov (aerial image of the Venice Estuary)

Venice (Venezia) The Dese Estuary is one of the lagoons of Venice, Italy – it is the largest in all of Italy (Maggiore and Keppel 2007) As a result of its location in the northern part of the Adriatic Sea, confinement is a key aspect for biological organisms and water quality There are four basins in Venice and three inlets that provide exchange to the Adriatic Sea (Solidoro et al. 2004)

Venice Bathymetry of the estuary of Venice as it opens into the North Adriatic Sea. Roland et al. 2009

Venice Tidal fluxes based on location in N. Adriatic Sea (Roland et al. 2009)

Venice Storm surge at Venice based upon wave height and movement of water into the upper Adriatic Sea Roland et al. 2009

Venice A city with sea level issues (here) Human influences go back hundreds of years and include constant management, thus “human-caused” introduction of species There are over 30 species alone that are considered invasive (Ambrogi 2000).

Venice “Crassostrea gigas (Pacific oyster) and the clam Tapes philippinarum have been imported in the lagoon in order to replace two species of bivalves that had undergone severe reductions in population” (Occhipinti-Ambrogi and Savini 2004)

The invasive cycle… The introduced Pacific oyster has led to a shift in the algal community… Here are some non-native algae species that are taking over the canals throughout Venice… Undaria pinnatifida, Sargassum muticum and Antithamnion pectinatum

Some of the invasive algal types

Managing Venice There are efforts to reduce non-native species including invertebrates like bryozoans that are tolerant to the lower salinities Sea level rise a major threat and recognizing flooding threats are a priority A healthy system can reduce the threat on non-native and invasive species

Tijuana Estuary, Mexico Primarily a shallow water habitat, though it is often termed an "intermittent estuary," as it is subjected to extreme changes in streamflow at different times of the year (National Estuary Program, 2008). Changes in the tidal flow have caused a decline in diversity of species in that the habitat has been altered much like 90 percent of the wetlands habitat across southern California (Zedler et al., 2001)

Tijuana As a result of increased salinity, it is considered a negative estuary Extreme hypersalinity from is more characteristic of higher elevations with less frequent tidal inundation (Noe and Zedler, 2001). Decrease in freshwater inputs and changes in seasonal weather patterns, the Tijuana watershed has been drier and the mean salinity has increased (see the following figure from Zedler et al., 2001).

Tijuana Estuary In comparison to other estuarine systems, the lack of outflow water creates a high percentage of hypoxia in the Tijuana estuary, 25.2% – 30.2% (Wenner et al. 2004) In southern California, prior to development, approximately seven creeks and river tributaries provided freshwater flows into the San Diego Bay.

How would you help the estuary? Please discuss how you would aid an estuary that has negative estuary characteristics….