A STUDY BY Justin Sellers * Robin Rodriguez * James Lee
SUCCESSION IS A COMMON OCCURANCE IN MOST TERRESTRIAL HABITATS. SUCCESSION FROM LICHENS TO EVERGREEN TREES, FOR EXAMPLE, OR FROM ANY BASIC LIFE TO A CLIMAX COMMUNITY. BUT WHAT ABOUT AQUATIC HABITATS? MORE SPECIFICALLY, WHAT ABOUT OUR LOCAL CREEK, THE ARROYO DEL VALLE? DOES SUCCESSION OCCUR AT THE MICROHABITAT LEVEL IN THE ARROYO DEL VALLE? WE SEE NO REASON WHY IT SHOULDN'T, AND BELIEVE THAT SUCCESSION SHOULD OCCUR THERE AS IT DOES ON LAND.
HYPOTHESIS:
IF SUCCESSION OCCURS AT THE MICROHABITAT LEVEL IN THE ARROYO DEL VALLE, THEN WE SHOULD SEE MORE AND MORE ADVANCED ORGANISMS EACH TIME WE RETRIEVE CAGES FROM THE CREEK.
PROCEDURE: WE HAVE CONSTRUCTED EIGHT METAL CAGES WHICH ARE APPROXIMATELY
12" X 3" X 3" IN SIZE .
IN ORDER TO PERFORM OUR EXPERIMENT AND MAKE THE CAGES WE USED: FOR THE CAGES:Wire Cutters, 9 sq. ft. of screen, 1 roll of steel wire. FOR THE EXPERIMENT: pH Paper, A Thermometer, A Large (about 5-gallon) paint bucket, Light and Dissecting Microscopes, and a journal to record all of our findings
THE CAGES HAVE BEEN WEIGHED DOWN BY AN EQUAL QUANTITY OF ROCKS. THEY WERE PLACED IN THE SPECIFIED AREA OF THE ARROYO DEL VALLE. ON ANY DAY WHEN WE VISITED THE CREEK, WE "PULLED" ONE OR MORE CAGES FROM THE WATER AND TRANSPORTED IT BACK TO MR. THEIL'S ROOM IN A LARGE, PLASTIC PAINT BUCKET FILLED WITH CREEK WATER.
WE ORIGINALLY PLACED THE CAGES IN THE CREEK ON WEDNESDAY, APRIL 16, 1997 AND WE MONITORED THE AREA PERIODICALLY. EACH TIME WE WENT DOWN TO THE CREEK, ONE OR MORE CAGES WERE PULLED FROM THE WATER, PHOTOGRAPHED, AND ITS CONTENTS AND ANY CHAGES IN ITS ENVIORNMENT WERE EVALUATED AND RECORDED.
THE WATER IN THE PLACE WE CHOSE RANGED FROM 10 TO 20 DEGRESS CELSIUS. IT WAS USUALLY ABOUT 30-40 CENTIMETERS DEEP, WITH A NEUTRAL PH AND SECLUDED FROM THE REGULAR PATH.WHEN THE CAGES WERE RETRIEVED, WE USED MICROSCOPES AND FIELD GUIDES IN ORDER TO CLASSIFY ANY ORGANISMS WE FOUND.
FOR THE ACTUAL EXPERIMENT, JUSTIN PURCHASED NINE SQUARE FEET OF SCREEN AND A ROLL OF WIRE. THE EIGHT CAGES WERE CONSTRUCTED AND SCHEDULED TO BE PLACED THE NEXT DAY. UNFORTUNATELY, THE FIRST AREA WE CHOSE WAS NOT A FAVORABLE LOCATION, SO THE CAGES HAD TO BE MOVED. DURING THE MOVE, HOWEVER, ALL BUT THREE OF THE NOT-SO-WELL BUILT CAGES FELL APART. THOSE THREE WERE PLACED, AND THE REST TAKEN BACK TO BE REBUILT. DUE TO UNPREDICTABLE OCCURENCES, ANOTHER ROLL OF WIRE HAD TO BE PURCHASED, AND JUSTIN USED IT TO BETTER REINFORCE AND REPAIR THE BROKEN CAGES.
THOSE CAGES WERE THEN PLACED NEXT TO OTHER THREE, EACH FILLED WITH THE APPROXIMATE AMOUNTS OF ROCKS. AFTER SIX DAYS, ONE CAGE WAS TAKEN FROM THE CREEK TO BE STUDIED.
THE WATER WAS ABOUT 17 DEGREES CELSIUS AND HALF A METER DEEP, AND IT WAS STILL NEUTRAL. IT WAS A COOL DAY, ABOUT 29 DEGREES CELSIUS. ALGAE HUNG OFF THE CAGE, BUT THE ROCKS WERE WHAT WE WERE REALLY INTERESTED IN. USING A DISECTING MICROSCOPE AND A LIGHT MICROSCOPE, WE STUDIED THE ROCKS IN HOPES OF FINDING ANY TINY ORGANISMS WHICH MIGHT HAVE BEEN ON THE ROCKS.
THE ROCKS WERE COVERED WITH MANY SMALL, LONG STRANDS. UNDER THE MICROSCOPES, THESE STRANDS RESEMBLED TINY SAUSAGES, REALLY A TYPE OF BROWN ALGAE. THIS IS COMMON IN OUR AREA SINCE EVERY TIME WE RETURNED WE FOUND MORE AND MORE OF IT. WE ALSO FOUND A SMALL SNAIL- LIKE NAUTILUS SHELL. ANOTHER THING ON ONE OF THE ROCKS WAS A BROWNISH BALL OF SLIME. WHEN VIEWED UNDER THE LIGHT MICROSCOPE, PROTOZOANS COULD BE SEEN.
TWO DAYS LATER, WHEN WE RETURNED TO THE CREEK, THE WATER HAD RECEEDED TO ABOUT A QUARTER OF A METER DEEP AND THE WATER TEMPERATURE WAS CLOSE TO 20 DEGREES CELSIUS. UNFORTUNATELY, THE CAGE HAD BEEN DAMAGED AND CONTAINED BUT TWO ROCKS. THAT DAY, JAMES AND JUSTIN STAYED AFTER SCHOOL TO STUDY THE CAGE AND THE ROCKS WHICH HAD BEEN IN THE CREEK FOR EIGHT DAYS. THIS TIME MANY MORE ORGANISMS WERE FOUND THAN IN THE FIRST CAGE. A LOT MORE BROWN ALGAE WAS FOUND, NICKNAMED "SAUSAGE ALGAE" BECAUSE OF ITS APPEARANCE. ANOTHER GYRALOUS SNAIL SHELL AND THREE SMALL WORMS. ONE RED, ONE GRAY, AND ONE BROWN. THE APPEARANCE OF MORE ORGANISMS THIS TIME STRENGTHEN OUR HYPOTHESIS THAT WE SHOULD SEE MORE IN THE FUTURE.
AS OUR EXPERIMENT WENT ON, WE DID NOTICE MORE AND MORE ADVANCED CREATURES IN OUR "COMMUNITY". WE BEGAN TO NOTICE PLANARIAN OR FLATWORMS IN OUR CAGES STARTING ON MAY 1: 16 DAYS AFTER THE CAGES WERE ORGINALLY DROPPED. WITH LESS THAN TWO WEEKS LEFT TO OUR DEADLINE ON MAY 12, WE DECIDED TO REMOVE TWO CAGES AT A TIME UNTIL WE HAD PULLED ALL EIGHT. WHEN WE RETURNED TO THE CREEK THE NEXT DAY, IT WAS WARMER AND THE WATER HAD RECEEDED SLIGHTLY, BUT THE PH AND TEMPERATURE REMAINED THE SAME. AFTER SCHOOL THAT DAY, JUSTIN STAYED TO ANALYZE THE TWO CAGES AND FOUND A GREAT WEALTH OF ORGANISMS. HE FOUND OUR STANDARD "SAUSAGE" ALGAE, MORE FLATWORMS, MORE GYRALUS SHELLS, BUT THIS TIME HE FOUND A DIFFERENT TYPE OF NAUTILUS SHELL: IDENTIFIED BY ROBIN AS A "BYTHINIA" SHELL. ON SOME OF THE OTHER ROCKS WERE PLANARIANS AND SOME OTHER CLEAR WORMS. BY ANALYZING SOME OTHER OBJECTS, HE WAS ABLE TO SEE SEVERAL LIVING PROTISTS IN THE WATER. TO ALL OF OUR SUPRISE, WE FOUND THAT WE WERE SUPPORTING A COMPLEX COMMUNITY WHEN JUSTIN FOUND THREE TINY BEETLE-LIKE OBJECTS AND WHAT APPEARED TO BE AN IMMATURE INSECT OF SOME KIND.
OUR CONSTANT OBSERVATIONS DID NOT HALT AT IDENTIFYING OUR ORGANISMS. DURING OUR TIME AT THE ARROYO DEL VALLE, WE MONITORED SEVERAL FACTORS, PRESENTED HERE IN GRAPHS OF WATER TEMPERATURE AND THE AMOUNT OF IDENTIFIABLE ORGANISMS RETIEVED IN OUR CAGES.
OUR CONFIDENCE IN OUR HYPOTHESIS HAS ONLY INCREASED SINCE THE COMMENCEMENT OF OUR OBSERVATIONS. WE HAVE NOTICED SINCE THE IDENTIFICATION OF ONLY ALGAE TO SEVERAL INSECTS THAT WE HAVE SUPPORTED A COMPLEX COMMUNITY IN OUR LOCAL CREEK. THE SMALL BAY WHICH WE OBSERVED IN THE ARROYO DEL VALLE HAS MATURED IN THE PAST FOUR WEEKS WITH THE COMING OF SPRING AND WE WERE THERE TO WITNESS AND RECORD IT. WE ARE PROUD FOR THE SUCCESS OF OUR EXPERIMENT MAINLY BECAUSE WE HAD VERY LITTLE TO BASE OUR OBSERVATIONS ON. THE LITTLE INFORMATION AVAILABLE ON SUCCESSION DIDN'T EVEN MENTION AQUATIC HABITATS AND WE WERE LEFT TO OUR OWN WITS. HOWEVER, AS THE AMOUNT OF ORGANISMS AND THEIR COMPLEXITY BECAME PREVALENT, WE KNOW THAT OUR HYPOTHESIS IS STRONG AND CAN BE USED FOR FUTURE OBSERVERS OF PLEASANTON'S ARROYO DEL VALLE AND CREEKS AND WATER HABITATS EVERYWHERE
