Preparation: Once you have located a tidal wetland to study, the use of aerial photography through Google Map or Earth is a fun and effective way to motivate students in learning about their local environment. Exploration of the tidal wetland of interest becomes more meaningful in a geographic context in relation to students’ experiences. Students should spend some time remotely navigating the Hudson Estuary on Google Earth or Maps. GIS maps of wetland vegetation may be available from Cary Institute for Ecosystem Studies which can then be printed and laminated. Copies of booklet “Hudson River Field Guide to Plants of Freshwater Tidal Wetlands” may still be available from NYSDEC or check local nature preserves or organizations in your area. Your field study plan will vary depending on available equipment (kayaks, water testing instruments, etc.) and the nature of the terrain around your site. For comparisons with long term data on water chemistry at your site, contact Stuart Findlay at the Cary Institute of Ecosystem Studies.
Engage: Ask students what wetlands are and to name as many types as they can with local examples. Ask them what values wetlands provide. Compile student answers on board. Give "Wetlands" reading assignment and question worksheet. Discuss wetland types (tidal vs. nontidal) and their values using Powerpoint Presentation (PPT) for the lesson. Show them map of Significant Biodiversity Areas of the Hudson River Estuary Corridor showing distribution of both tidal and non-tidal wetlands. On their copies of the map (from their handout) have them label the major tributaries of the Hudson and note the location of your study site.
Preparation for "What lives in different parts of a tidal marsh"? Provide each group of students with three envelopes and cut strips of organisms that live in each zone: submerged, broadleaf, and graminoid vegetation. You may want to laminate these for future use.
Explore:
Activity 1: Study Site Location and Tide Dynamics:
Students will explore the study site on Google Earth and compare with laminated aerial photo of site. First, using the powerpoint show students a map and images of the Hudson Estuary watershed and show them the location of your wetland study site. Then have them log onto Google Earth and navigate to the study site and play with the scale. Let them explore other areas throughout the estuary (time permitting) to develop geographic perspective. Have a brief discussion on the geography of the estuary watershed having students name notable features (including names of major tributaries).
Using the laminated photo of the wetland site have students use a red marker to draw an arrow in the river showing drainage direction to the ocean as well as arrows showing tidal flux in and out of the wetland. Review the dynamics of tides w/PPT and how the lunar cycle affects the tides, including the difference between neap and spring tides. Explain to students the movement of various solutes and suspended material in the tidewater that may affect the tidal wetland ecosystem. Challenge students to identify types of ecologically important solutes (i.e. nutrients, dissolved oxygen, salts, etc.) and suspended solids (inorganic and organic). Discuss sedimentation and substrate elevations within their site’s geography.
Activity 2: Tidal Plant Communities:
Pre-field trip: Provide students with the worksheet “What lives in different parts of a tidal marsh?” Have them read and complete part I of the activity then discuss the three major vegetation zones using projected images and elicit reasons for such plant distribution.
Do the part II group biodiversity activity with the envelopes and record results on the board. Expand on the activity by having students learn to identify the plants from the results of their activity by examining copies of the NYSDEC booklet. Afterward, project images (from the PPT ) of the most common tidal plants and have students identify the common name and the tidal zone it most likely it inhabits.
Have students make predictions of locations of vegetative zones from the aerial photos. Give students aerial photos of the study site, a clipboard and permanent colored markers, then have them place a transparency sheet over the photo, clip on a clipboard and use the markers to delineate the zones and include a legend. Students can then later compare their predictions to observations on field study as well as comparing with published data.
(Optional) Challenge students to provide examples and rationale for different plant species’ morphological adaptations with respect to the tides as a limiting factor.
Field trip: Students working in small groups will identify the tidal zones and vegetation types at different sites. Students will circumnavigate the wetland on foot if possible (or enter the wetland using canoes/kayaks to paddle into the wetland) stopping at various vantage points to observe and denote their data (see data sheets). At each site observed, students are to mark on their aerial photos locations of sites in red marker, and attempt to delineate with the markers the various intertidal vegetative zones observed.
Post Field Trip: Students will compare their vegetation results with the Cary Institute GIS map of wetland vegetation for the study site as well as their own predictions.
Activity 3: Nutrient Uptake During the Ebb Phase in a Tidal Wetland
This portion of the study will have required prior instruction in water chemistry and the role of nitrogen in biomass production. If possible students should have a background in biogeochemical cycling of nitrogen (as well as other elements). At the very least students should understand inorganic and organic forms of nitrogen and that nitrate and ammonium ions are the macronutrient sources of nitrogen for all plants and algae.
Pre-field trip: After discussing the tidal flux of water and materials in the wetland, students are to pose hypotheses (and rationale) to the question “Do freshwater tidal wetlands significantly absorb nitrogen during the ebb phase of the tidal cycle? Have them record in their worksheets.
Elicit from students what type of study design would be effective to investigate the scientific problem. Come to a class consensus on a study involving samples taken in various zones of the wetland right after high tide and then 3 hours after. Focus of study should be on nitrogen in its two most absorbed forms, nitrate and ammonium (depending upon instrumentation available). Additional parameters such as Temperature and Dissolved Oxygen (as well as percent DO saturation) can optionally be tested. Students need to be proficient in use of water quality instrumentation prior to testing.
Field-trip: Samples to be collected by volunteers by kayak/canoe. Collected samples can either be tested immediately or kept on ice/refrigerated and analyzed within 48 hours. Proper protocol in analyses is to be emphasized. The locations of sampling sites are to be noted on the aerial photos.
Post-field trip: Students evaluate chemical results and draw conclusions. Comparisons can be made with published data if available.
Explain:
After students have collected data and made comparisons, discuss their findings. Do their plant observations correlate with the GIS map and their own predictions? Did their nutrient test results support their hypotheses? Did oxygen or temperature change much during the ebb phase? Do their results resemble patterns found in published data? Ask students to think about the ecological dynamics occurring in relation to all variables observed and how their results should reflect these dynamics. If results appear to be confusing and unexpected, elicit possible reasons for such results.
Extend: Students can explore the possible effects global warming will have on Hudson River tidal wetlands by completing the on-line activity “Hudson River Wetlands: Will they Disappear?” (Cary Institute). Have students’ complete worksheet and discuss after all students complete the assignment.
Evaluate: Students turn in the lab report and activity worksheets
